The SEV-SNP specification provides the guest a mechanism to communicate
with the PSP without risk from a malicious hypervisor who wishes to
read, alter, drop or replay the messages sent. The driver uses
snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or
SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP.
The PSP requires that all communication should be encrypted using key
specified through the platform_data.
Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation
report.
The {alloc_free}_shared_pages() is used for allocating the shared buffer
used by the driver to communicate with the PSP. Later patches will use
it to allocate the certificate blob and more.
See SEV-SNP spec section Guest Messages for more details.
Signed-off-by: Brijesh Singh <[email protected]>
---
Documentation/virt/coco/sevguest.rst | 86 ++++
Documentation/virt/index.rst | 1 +
drivers/virt/Kconfig | 3 +
drivers/virt/Makefile | 1 +
drivers/virt/coco/sevguest/Kconfig | 14 +
drivers/virt/coco/sevguest/Makefile | 2 +
drivers/virt/coco/sevguest/sevguest.c | 607 ++++++++++++++++++++++++++
drivers/virt/coco/sevguest/sevguest.h | 98 +++++
include/uapi/linux/sev-guest.h | 50 +++
9 files changed, 862 insertions(+)
create mode 100644 Documentation/virt/coco/sevguest.rst
create mode 100644 drivers/virt/coco/sevguest/Kconfig
create mode 100644 drivers/virt/coco/sevguest/Makefile
create mode 100644 drivers/virt/coco/sevguest/sevguest.c
create mode 100644 drivers/virt/coco/sevguest/sevguest.h
create mode 100644 include/uapi/linux/sev-guest.h
diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
new file mode 100644
index 000000000000..34feff6d5940
--- /dev/null
+++ b/Documentation/virt/coco/sevguest.rst
@@ -0,0 +1,86 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+The Definitive SEV Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The SEV API is a set of ioctls that are used by the guest or hypervisor
+to get or set a certain aspect of the SEV virtual machine. The ioctls belong
+to the following classes:
+
+ - Hypervisor ioctls: These query and set global attributes which affect the
+ whole SEV firmware. These ioctl are used by platform provisioning tools.
+
+ - Guest ioctls: These query and set attributes of the SEV virtual machine.
+
+2. API description
+==================
+
+This section describes ioctls that is used for querying the SEV guest report
+from the SEV firmware. For each ioctl, the following information is provided
+along with a description:
+
+ Technology:
+ which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
+
+ Type:
+ hypervisor or guest. The ioctl can be used inside the guest or the
+ hypervisor.
+
+ Parameters:
+ what parameters are accepted by the ioctl.
+
+ Returns:
+ the return value. General error numbers (-ENOMEM, -EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
+The ioctl accepts struct snp_user_guest_request. The input and output structure is
+specified through the req_data and resp_data field respectively. If the ioctl fails
+to execute due to a firmware error, then fw_err code will be set otherwise the
+fw_err will be set to 0x00000000000000ff.
+
+The firmware checks that the message sequence counter is one greater than
+the guests message sequence counter. If guest driver fails to increment message
+counter (e.g counter overflow), then -EIO will be returned.
+
+::
+
+ struct snp_guest_request_ioctl {
+ /* Message version number */
+ __u32 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* firmware error code on failure (see psp-sev.h) */
+ __u64 fw_err;
+ };
+
+2.1 SNP_GET_REPORT
+------------------
+
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_REPORT ioctl can be used to query the attestation report from the
+SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
+provided by the SEV-SNP firmware to query the attestation report.
+
+On success, the snp_report_resp.data will contains the report. The report
+contain the format described in the SEV-SNP specification. See the SEV-SNP
+specification for further details.
+
+
+Reference
+---------
+
+SEV-SNP and GHCB specification: developer.amd.com/sev
+
+The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
diff --git a/Documentation/virt/index.rst b/Documentation/virt/index.rst
index edea7fea95a8..40ad0d20032e 100644
--- a/Documentation/virt/index.rst
+++ b/Documentation/virt/index.rst
@@ -13,6 +13,7 @@ Linux Virtualization Support
guest-halt-polling
ne_overview
acrn/index
+ coco/sevguest
.. only:: html and subproject
diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 8061e8ef449f..e457e47610d3 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -36,4 +36,7 @@ source "drivers/virt/vboxguest/Kconfig"
source "drivers/virt/nitro_enclaves/Kconfig"
source "drivers/virt/acrn/Kconfig"
+
+source "drivers/virt/coco/sevguest/Kconfig"
+
endif
diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
index 3e272ea60cd9..9c704a6fdcda 100644
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -8,3 +8,4 @@ obj-y += vboxguest/
obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
obj-$(CONFIG_ACRN_HSM) += acrn/
+obj-$(CONFIG_SEV_GUEST) += coco/sevguest/
diff --git a/drivers/virt/coco/sevguest/Kconfig b/drivers/virt/coco/sevguest/Kconfig
new file mode 100644
index 000000000000..74ca1fe09437
--- /dev/null
+++ b/drivers/virt/coco/sevguest/Kconfig
@@ -0,0 +1,14 @@
+config SEV_GUEST
+ tristate "AMD SEV Guest driver"
+ default m
+ depends on AMD_MEM_ENCRYPT
+ select CRYPTO_AEAD2
+ select CRYPTO_GCM
+ help
+ SEV-SNP firmware provides the guest a mechanism to communicate with
+ the PSP without risk from a malicious hypervisor who wishes to read,
+ alter, drop or replay the messages sent. The driver provides
+ userspace interface to communicate with the PSP to request the
+ attestation report and more.
+
+ If you choose 'M' here, this module will be called sevguest.
diff --git a/drivers/virt/coco/sevguest/Makefile b/drivers/virt/coco/sevguest/Makefile
new file mode 100644
index 000000000000..b1ffb2b4177b
--- /dev/null
+++ b/drivers/virt/coco/sevguest/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SEV_GUEST) += sevguest.o
diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
new file mode 100644
index 000000000000..97b98a3f5f89
--- /dev/null
+++ b/drivers/virt/coco/sevguest/sevguest.c
@@ -0,0 +1,607 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Secure Encrypted Virtualization Nested Paging (SEV-SNP) guest request interface
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ */
+
+#define pr_fmt(fmt) "SNP: GUEST: " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/miscdevice.h>
+#include <linux/set_memory.h>
+#include <linux/fs.h>
+#include <crypto/aead.h>
+#include <linux/scatterlist.h>
+#include <linux/psp-sev.h>
+#include <uapi/linux/sev-guest.h>
+#include <uapi/linux/psp-sev.h>
+
+#include <asm/svm.h>
+#include <asm/sev.h>
+
+#include "sevguest.h"
+
+#define DEVICE_NAME "sev-guest"
+#define AAD_LEN 48
+#define MSG_HDR_VER 1
+
+struct snp_guest_crypto {
+ struct crypto_aead *tfm;
+ u8 *iv, *authtag;
+ int iv_len, a_len;
+};
+
+struct snp_guest_dev {
+ struct device *dev;
+ struct miscdevice misc;
+
+ struct snp_guest_crypto *crypto;
+ struct snp_guest_msg *request, *response;
+ struct snp_secrets_page_layout *layout;
+ struct snp_req_data input;
+ u32 *os_area_msg_seqno;
+ u8 *vmpck;
+};
+
+static u32 vmpck_id;
+module_param(vmpck_id, uint, 0444);
+MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
+
+/* Mutex to serialize the shared buffer access and command handling. */
+static DEFINE_MUTEX(snp_cmd_mutex);
+
+static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
+{
+ char zero_key[VMPCK_KEY_LEN] = {0};
+
+ if (snp_dev->vmpck)
+ return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
+
+ return true;
+}
+
+static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
+{
+ memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
+ snp_dev->vmpck = NULL;
+}
+
+static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ /* Read the current message sequence counter from secrets pages */
+ count = *snp_dev->os_area_msg_seqno;
+
+ return count + 1;
+}
+
+/* Return a non-zero on success */
+static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count = __snp_get_msg_seqno(snp_dev);
+
+ /*
+ * The message sequence counter for the SNP guest request is a 64-bit
+ * value but the version 2 of GHCB specification defines a 32-bit storage
+ * for it. If the counter exceeds the 32-bit value then return zero.
+ * The caller should check the return value, but if the caller happens to
+ * not check the value and use it, then the firmware treats zero as an
+ * invalid number and will fail the message request.
+ */
+ if (count >= UINT_MAX) {
+ pr_err_ratelimited("request message sequence counter overflow\n");
+ return 0;
+ }
+
+ return count;
+}
+
+static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ /*
+ * The counter is also incremented by the PSP, so increment it by 2
+ * and save in secrets page.
+ */
+ *snp_dev->os_area_msg_seqno += 2;
+}
+
+static inline struct snp_guest_dev *to_snp_dev(struct file *file)
+{
+ struct miscdevice *dev = file->private_data;
+
+ return container_of(dev, struct snp_guest_dev, misc);
+}
+
+static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
+{
+ struct snp_guest_crypto *crypto;
+
+ crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
+ if (!crypto)
+ return NULL;
+
+ crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
+ if (IS_ERR(crypto->tfm))
+ goto e_free;
+
+ if (crypto_aead_setkey(crypto->tfm, key, keylen))
+ goto e_free_crypto;
+
+ crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
+ crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->iv)
+ goto e_free_crypto;
+
+ if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
+ if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
+ dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
+ goto e_free_iv;
+ }
+ }
+
+ crypto->a_len = crypto_aead_authsize(crypto->tfm);
+ crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->authtag)
+ goto e_free_auth;
+
+ return crypto;
+
+e_free_auth:
+ kfree(crypto->authtag);
+e_free_iv:
+ kfree(crypto->iv);
+e_free_crypto:
+ crypto_free_aead(crypto->tfm);
+e_free:
+ kfree(crypto);
+
+ return NULL;
+}
+
+static void deinit_crypto(struct snp_guest_crypto *crypto)
+{
+ crypto_free_aead(crypto->tfm);
+ kfree(crypto->iv);
+ kfree(crypto->authtag);
+ kfree(crypto);
+}
+
+static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
+ u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
+{
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+ struct scatterlist src[3], dst[3];
+ DECLARE_CRYPTO_WAIT(wait);
+ struct aead_request *req;
+ int ret;
+
+ req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
+ if (!req)
+ return -ENOMEM;
+
+ /*
+ * AEAD memory operations:
+ * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
+ * | msg header | plaintext | hdr->authtag |
+ * | bytes 30h - 5Fh | or | |
+ * | | cipher | |
+ * +------------------+------------------+----------------+
+ */
+ sg_init_table(src, 3);
+ sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&src[1], src_buf, hdr->msg_sz);
+ sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
+
+ sg_init_table(dst, 3);
+ sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
+ sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
+
+ aead_request_set_ad(req, AAD_LEN);
+ aead_request_set_tfm(req, crypto->tfm);
+ aead_request_set_callback(req, 0, crypto_req_done, &wait);
+
+ aead_request_set_crypt(req, src, dst, len, crypto->iv);
+ ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
+
+ aead_request_free(req);
+ return ret;
+}
+
+static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
+}
+
+static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ /* Build IV with response buffer sequence number */
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
+}
+
+static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg *resp = snp_dev->response;
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *req_hdr = &req->hdr;
+ struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
+
+ dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
+ resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
+
+ /* Verify that the sequence counter is incremented by 1 */
+ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
+ return -EBADMSG;
+
+ /* Verify response message type and version number. */
+ if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
+ resp_hdr->msg_version != req_hdr->msg_version)
+ return -EBADMSG;
+
+ /*
+ * If the message size is greater than our buffer length then return
+ * an error.
+ */
+ if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
+ return -EBADMSG;
+
+ /* Decrypt the payload */
+ return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
+}
+
+static bool enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
+ void *payload, size_t sz)
+{
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *hdr = &req->hdr;
+
+ memset(req, 0, sizeof(*req));
+
+ hdr->algo = SNP_AEAD_AES_256_GCM;
+ hdr->hdr_version = MSG_HDR_VER;
+ hdr->hdr_sz = sizeof(*hdr);
+ hdr->msg_type = type;
+ hdr->msg_version = version;
+ hdr->msg_seqno = seqno;
+ hdr->msg_vmpck = vmpck_id;
+ hdr->msg_sz = sz;
+
+ /* Verify the sequence number is non-zero */
+ if (!hdr->msg_seqno)
+ return -ENOSR;
+
+ dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
+ hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
+
+ return __enc_payload(snp_dev, req, payload, sz);
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
+ u8 type, void *req_buf, size_t req_sz, void *resp_buf,
+ u32 resp_sz, __u64 *fw_err)
+{
+ unsigned long err;
+ u64 seqno;
+ int rc;
+
+ /* Get message sequence and verify that its a non-zero */
+ seqno = snp_get_msg_seqno(snp_dev);
+ if (!seqno)
+ return -EIO;
+
+ memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+ /* Encrypt the userspace provided payload */
+ rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+ if (rc)
+ return rc;
+
+ /* Call firmware to process the request */
+ rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+ if (fw_err)
+ *fw_err = err;
+
+ if (rc)
+ return rc;
+
+ /*
+ * The verify_and_dec_payload() will fail only if the hypervisor is
+ * actively modifying the message header or corrupting the encrypted payload.
+ * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
+ * the key cannot be used for any communication. The key is disabled to ensure
+ * that AES-GCM does not use the same IV while encrypting the request payload.
+ */
+ rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
+ if (rc) {
+ dev_alert(snp_dev->dev,
+ "Detected unexpected decode failure, disabling the vmpck_id %d\n",
+ vmpck_id);
+ snp_disable_vmpck(snp_dev);
+ return rc;
+ }
+
+ /* Increment to new message sequence after payload decryption was successful. */
+ snp_inc_msg_seqno(snp_dev);
+
+ return 0;
+}
+
+static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_report_resp *resp;
+ struct snp_report_req req;
+ int rc, resp_len;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ if (!arg->req_data || !arg->resp_data)
+ return -EINVAL;
+
+ if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
+ return -EFAULT;
+
+ /*
+ * The intermediate response buffer is used while decrypting the
+ * response payload. Make sure that it has enough space to cover the
+ * authtag.
+ */
+ resp_len = sizeof(resp->data) + crypto->a_len;
+ resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
+ if (!resp)
+ return -ENOMEM;
+
+ rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+ SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
+ resp_len, &arg->fw_err);
+ if (rc)
+ goto e_free;
+
+ if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
+ rc = -EFAULT;
+
+e_free:
+ kfree(resp);
+ return rc;
+}
+
+static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
+{
+ struct snp_guest_dev *snp_dev = to_snp_dev(file);
+ void __user *argp = (void __user *)arg;
+ struct snp_guest_request_ioctl input;
+ int ret = -ENOTTY;
+
+ if (copy_from_user(&input, argp, sizeof(input)))
+ return -EFAULT;
+
+ input.fw_err = 0xff;
+
+ /* Message version must be non-zero */
+ if (!input.msg_version)
+ return -EINVAL;
+
+ mutex_lock(&snp_cmd_mutex);
+
+ /* Check if the VMPCK is not empty */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
+ mutex_unlock(&snp_cmd_mutex);
+ return -ENOTTY;
+ }
+
+ switch (ioctl) {
+ case SNP_GET_REPORT:
+ ret = get_report(snp_dev, &input);
+ break;
+ default:
+ break;
+ }
+
+ mutex_unlock(&snp_cmd_mutex);
+
+ if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
+ return -EFAULT;
+
+ return ret;
+}
+
+static void free_shared_pages(void *buf, size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ int ret;
+
+ if (!buf)
+ return;
+
+ ret = set_memory_encrypted((unsigned long)buf, npages);
+ if (ret) {
+ WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
+ return;
+ }
+
+ __free_pages(virt_to_page(buf), get_order(sz));
+}
+
+static void *alloc_shared_pages(size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ struct page *page;
+ int ret;
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
+ if (IS_ERR(page))
+ return NULL;
+
+ ret = set_memory_decrypted((unsigned long)page_address(page), npages);
+ if (ret) {
+ pr_err("failed to mark page shared, ret=%d\n", ret);
+ __free_pages(page, get_order(sz));
+ return NULL;
+ }
+
+ return page_address(page);
+}
+
+static const struct file_operations snp_guest_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = snp_guest_ioctl,
+};
+
+static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
+{
+ u8 *key = NULL;
+
+ switch (id) {
+ case 0:
+ *seqno = &layout->os_area.msg_seqno_0;
+ key = layout->vmpck0;
+ break;
+ case 1:
+ *seqno = &layout->os_area.msg_seqno_1;
+ key = layout->vmpck1;
+ break;
+ case 2:
+ *seqno = &layout->os_area.msg_seqno_2;
+ key = layout->vmpck2;
+ break;
+ case 3:
+ *seqno = &layout->os_area.msg_seqno_3;
+ key = layout->vmpck3;
+ break;
+ default:
+ break;
+ }
+
+ return key;
+}
+
+static int __init snp_guest_probe(struct platform_device *pdev)
+{
+ struct snp_secrets_page_layout *layout;
+ struct snp_guest_platform_data *data;
+ struct device *dev = &pdev->dev;
+ struct snp_guest_dev *snp_dev;
+ struct miscdevice *misc;
+ int ret;
+
+ if (!dev->platform_data)
+ return -ENODEV;
+
+ data = (struct snp_guest_platform_data *)dev->platform_data;
+ layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
+ if (!layout)
+ return -ENODEV;
+
+ ret = -ENOMEM;
+ snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
+ if (!snp_dev)
+ goto e_unmap;
+
+ ret = -EINVAL;
+ snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
+ if (!snp_dev->vmpck) {
+ dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ /* Verify that VMPCK is not zero. */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err(dev, "vmpck id %d is null\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ platform_set_drvdata(pdev, snp_dev);
+ snp_dev->dev = dev;
+ snp_dev->layout = layout;
+
+ /* Allocate the shared page used for the request and response message. */
+ snp_dev->request = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!snp_dev->request)
+ goto e_unmap;
+
+ snp_dev->response = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!snp_dev->response)
+ goto e_free_request;
+
+ ret = -EIO;
+ snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
+ if (!snp_dev->crypto)
+ goto e_free_response;
+
+ misc = &snp_dev->misc;
+ misc->minor = MISC_DYNAMIC_MINOR;
+ misc->name = DEVICE_NAME;
+ misc->fops = &snp_guest_fops;
+
+ /* initial the input address for guest request */
+ snp_dev->input.req_gpa = __pa(snp_dev->request);
+ snp_dev->input.resp_gpa = __pa(snp_dev->response);
+
+ ret = misc_register(misc);
+ if (ret)
+ goto e_free_response;
+
+ dev_info(dev, "Initialized SNP guest driver (using vmpck_id %d)\n", vmpck_id);
+ return 0;
+
+e_free_response:
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+e_free_request:
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+e_unmap:
+ iounmap(layout);
+ return ret;
+}
+
+static int __exit snp_guest_remove(struct platform_device *pdev)
+{
+ struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
+
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+ deinit_crypto(snp_dev->crypto);
+ misc_deregister(&snp_dev->misc);
+
+ return 0;
+}
+
+static struct platform_driver snp_guest_driver = {
+ .remove = __exit_p(snp_guest_remove),
+ .driver = {
+ .name = "snp-guest",
+ },
+};
+
+module_platform_driver_probe(snp_guest_driver, snp_guest_probe);
+
+MODULE_AUTHOR("Brijesh Singh <[email protected]>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0.0");
+MODULE_DESCRIPTION("AMD SNP Guest Driver");
diff --git a/drivers/virt/coco/sevguest/sevguest.h b/drivers/virt/coco/sevguest/sevguest.h
new file mode 100644
index 000000000000..d39bdd013765
--- /dev/null
+++ b/drivers/virt/coco/sevguest/sevguest.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ *
+ * SEV-SNP API spec is available at https://developer.amd.com/sev
+ */
+
+#ifndef __VIRT_SEVGUEST_H__
+#define __VIRT_SEVGUEST_H__
+
+#include <linux/types.h>
+
+#define MAX_AUTHTAG_LEN 32
+
+/* See SNP spec SNP_GUEST_REQUEST section for the structure */
+enum msg_type {
+ SNP_MSG_TYPE_INVALID = 0,
+ SNP_MSG_CPUID_REQ,
+ SNP_MSG_CPUID_RSP,
+ SNP_MSG_KEY_REQ,
+ SNP_MSG_KEY_RSP,
+ SNP_MSG_REPORT_REQ,
+ SNP_MSG_REPORT_RSP,
+ SNP_MSG_EXPORT_REQ,
+ SNP_MSG_EXPORT_RSP,
+ SNP_MSG_IMPORT_REQ,
+ SNP_MSG_IMPORT_RSP,
+ SNP_MSG_ABSORB_REQ,
+ SNP_MSG_ABSORB_RSP,
+ SNP_MSG_VMRK_REQ,
+ SNP_MSG_VMRK_RSP,
+
+ SNP_MSG_TYPE_MAX
+};
+
+enum aead_algo {
+ SNP_AEAD_INVALID,
+ SNP_AEAD_AES_256_GCM,
+};
+
+struct snp_guest_msg_hdr {
+ u8 authtag[MAX_AUTHTAG_LEN];
+ u64 msg_seqno;
+ u8 rsvd1[8];
+ u8 algo;
+ u8 hdr_version;
+ u16 hdr_sz;
+ u8 msg_type;
+ u8 msg_version;
+ u16 msg_sz;
+ u32 rsvd2;
+ u8 msg_vmpck;
+ u8 rsvd3[35];
+} __packed;
+
+struct snp_guest_msg {
+ struct snp_guest_msg_hdr hdr;
+ u8 payload[4000];
+} __packed;
+
+/*
+ * The secrets page contains 96-bytes of reserved field that can be used by
+ * the guest OS. The guest OS uses the area to save the message sequence
+ * number for each VMPCK.
+ *
+ * See the GHCB spec section Secret page layout for the format for this area.
+ */
+struct secrets_os_area {
+ u32 msg_seqno_0;
+ u32 msg_seqno_1;
+ u32 msg_seqno_2;
+ u32 msg_seqno_3;
+ u64 ap_jump_table_pa;
+ u8 rsvd[40];
+ u8 guest_usage[32];
+} __packed;
+
+#define VMPCK_KEY_LEN 32
+
+/* See the SNP spec version 0.9 for secrets page format */
+struct snp_secrets_page_layout {
+ u32 version;
+ u32 imien : 1,
+ rsvd1 : 31;
+ u32 fms;
+ u32 rsvd2;
+ u8 gosvw[16];
+ u8 vmpck0[VMPCK_KEY_LEN];
+ u8 vmpck1[VMPCK_KEY_LEN];
+ u8 vmpck2[VMPCK_KEY_LEN];
+ u8 vmpck3[VMPCK_KEY_LEN];
+ struct secrets_os_area os_area;
+ u8 rsvd3[3840];
+} __packed;
+
+#endif /* __VIRT_SEVGUEST_H__ */
diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h
new file mode 100644
index 000000000000..38f11d723c68
--- /dev/null
+++ b/include/uapi/linux/sev-guest.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
+/*
+ * Userspace interface for AMD SEV and SNP guest driver.
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ *
+ * SEV API specification is available at: https://developer.amd.com/sev/
+ */
+
+#ifndef __UAPI_LINUX_SEV_GUEST_H_
+#define __UAPI_LINUX_SEV_GUEST_H_
+
+#include <linux/types.h>
+
+struct snp_report_req {
+ /* user data that should be included in the report */
+ __u8 user_data[64];
+
+ /* The vmpl level to be included in the report */
+ __u32 vmpl;
+
+ /* Must be zero filled */
+ __u8 rsvd[28];
+};
+
+struct snp_report_resp {
+ /* response data, see SEV-SNP spec for the format */
+ __u8 data[4000];
+};
+
+struct snp_guest_request_ioctl {
+ /* message version number (must be non-zero) */
+ __u8 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* firmware error code on failure (see psp-sev.h) */
+ __u64 fw_err;
+};
+
+#define SNP_GUEST_REQ_IOC_TYPE 'S'
+
+/* Get SNP attestation report */
+#define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, struct snp_guest_request_ioctl)
+
+#endif /* __UAPI_LINUX_SEV_GUEST_H_ */
--
2.25.1
The following commit has been merged into the x86/sev branch of tip:
Commit-ID: fce96cf0443083e37455eff8f78fd240c621dae3
Gitweb: https://git.kernel.org/tip/fce96cf0443083e37455eff8f78fd240c621dae3
Author: Brijesh Singh <[email protected]>
AuthorDate: Mon, 07 Mar 2022 15:33:53 -06:00
Committer: Borislav Petkov <[email protected]>
CommitterDate: Thu, 07 Apr 2022 16:47:12 +02:00
virt: Add SEV-SNP guest driver
The SEV-SNP specification provides the guest a mechanism to communicate
with the PSP without risk from a malicious hypervisor who wishes to
read, alter, drop or replay the messages sent. The driver uses
snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or
SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP.
The PSP requires that all communication should be encrypted using key
specified through a struct snp_guest_platform_data descriptor.
Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation
report.
See SEV-SNP spec section Guest Messages for more details.
[ bp: Remove the "what" from the commit message, massage. ]
Signed-off-by: Brijesh Singh <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
Documentation/virt/coco/sevguest.rst | 86 ++++-
Documentation/virt/index.rst | 1 +-
drivers/virt/Kconfig | 3 +-
drivers/virt/Makefile | 1 +-
drivers/virt/coco/sevguest/Kconfig | 14 +-
drivers/virt/coco/sevguest/Makefile | 2 +-
drivers/virt/coco/sevguest/sevguest.c | 607 +++++++++++++++++++++++++-
drivers/virt/coco/sevguest/sevguest.h | 98 ++++-
include/uapi/linux/sev-guest.h | 50 ++-
9 files changed, 862 insertions(+)
create mode 100644 Documentation/virt/coco/sevguest.rst
create mode 100644 drivers/virt/coco/sevguest/Kconfig
create mode 100644 drivers/virt/coco/sevguest/Makefile
create mode 100644 drivers/virt/coco/sevguest/sevguest.c
create mode 100644 drivers/virt/coco/sevguest/sevguest.h
create mode 100644 include/uapi/linux/sev-guest.h
diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
new file mode 100644
index 0000000..3da782e
--- /dev/null
+++ b/Documentation/virt/coco/sevguest.rst
@@ -0,0 +1,86 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+The Definitive SEV Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The SEV API is a set of ioctls that are used by the guest or hypervisor
+to get or set a certain aspect of the SEV virtual machine. The ioctls belong
+to the following classes:
+
+ - Hypervisor ioctls: These query and set global attributes which affect the
+ whole SEV firmware. These ioctl are used by platform provisioning tools.
+
+ - Guest ioctls: These query and set attributes of the SEV virtual machine.
+
+2. API description
+==================
+
+This section describes ioctls that is used for querying the SEV guest report
+from the SEV firmware. For each ioctl, the following information is provided
+along with a description:
+
+ Technology:
+ which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
+
+ Type:
+ hypervisor or guest. The ioctl can be used inside the guest or the
+ hypervisor.
+
+ Parameters:
+ what parameters are accepted by the ioctl.
+
+ Returns:
+ the return value. General error numbers (-ENOMEM, -EINVAL)
+ are not detailed, but errors with specific meanings are.
+
+The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
+The ioctl accepts struct snp_user_guest_request. The input and output structure is
+specified through the req_data and resp_data field respectively. If the ioctl fails
+to execute due to a firmware error, then fw_err code will be set otherwise the
+fw_err will be set to 0x00000000000000ff.
+
+The firmware checks that the message sequence counter is one greater than
+the guests message sequence counter. If guest driver fails to increment message
+counter (e.g. counter overflow), then -EIO will be returned.
+
+::
+
+ struct snp_guest_request_ioctl {
+ /* Message version number */
+ __u32 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* firmware error code on failure (see psp-sev.h) */
+ __u64 fw_err;
+ };
+
+2.1 SNP_GET_REPORT
+------------------
+
+:Technology: sev-snp
+:Type: guest ioctl
+:Parameters (in): struct snp_report_req
+:Returns (out): struct snp_report_resp on success, -negative on error
+
+The SNP_GET_REPORT ioctl can be used to query the attestation report from the
+SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
+provided by the SEV-SNP firmware to query the attestation report.
+
+On success, the snp_report_resp.data will contains the report. The report
+contain the format described in the SEV-SNP specification. See the SEV-SNP
+specification for further details.
+
+
+Reference
+---------
+
+SEV-SNP and GHCB specification: developer.amd.com/sev
+
+The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
diff --git a/Documentation/virt/index.rst b/Documentation/virt/index.rst
index edea7fe..40ad0d2 100644
--- a/Documentation/virt/index.rst
+++ b/Documentation/virt/index.rst
@@ -13,6 +13,7 @@ Linux Virtualization Support
guest-halt-polling
ne_overview
acrn/index
+ coco/sevguest
.. only:: html and subproject
diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
index 121b929..7d3273c 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -47,4 +47,7 @@ source "drivers/virt/vboxguest/Kconfig"
source "drivers/virt/nitro_enclaves/Kconfig"
source "drivers/virt/acrn/Kconfig"
+
+source "drivers/virt/coco/sevguest/Kconfig"
+
endif
diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
index 108d0ff..7b87a7b 100644
--- a/drivers/virt/Makefile
+++ b/drivers/virt/Makefile
@@ -9,3 +9,4 @@ obj-y += vboxguest/
obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
obj-$(CONFIG_ACRN_HSM) += acrn/
+obj-$(CONFIG_SEV_GUEST) += coco/sevguest/
diff --git a/drivers/virt/coco/sevguest/Kconfig b/drivers/virt/coco/sevguest/Kconfig
new file mode 100644
index 0000000..74ca1fe
--- /dev/null
+++ b/drivers/virt/coco/sevguest/Kconfig
@@ -0,0 +1,14 @@
+config SEV_GUEST
+ tristate "AMD SEV Guest driver"
+ default m
+ depends on AMD_MEM_ENCRYPT
+ select CRYPTO_AEAD2
+ select CRYPTO_GCM
+ help
+ SEV-SNP firmware provides the guest a mechanism to communicate with
+ the PSP without risk from a malicious hypervisor who wishes to read,
+ alter, drop or replay the messages sent. The driver provides
+ userspace interface to communicate with the PSP to request the
+ attestation report and more.
+
+ If you choose 'M' here, this module will be called sevguest.
diff --git a/drivers/virt/coco/sevguest/Makefile b/drivers/virt/coco/sevguest/Makefile
new file mode 100644
index 0000000..b1ffb2b
--- /dev/null
+++ b/drivers/virt/coco/sevguest/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SEV_GUEST) += sevguest.o
diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
new file mode 100644
index 0000000..beda93c
--- /dev/null
+++ b/drivers/virt/coco/sevguest/sevguest.c
@@ -0,0 +1,607 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * AMD Secure Encrypted Virtualization Nested Paging (SEV-SNP) guest request interface
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ */
+
+#define pr_fmt(fmt) "SNP: GUEST: " fmt
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/io.h>
+#include <linux/platform_device.h>
+#include <linux/miscdevice.h>
+#include <linux/set_memory.h>
+#include <linux/fs.h>
+#include <crypto/aead.h>
+#include <linux/scatterlist.h>
+#include <linux/psp-sev.h>
+#include <uapi/linux/sev-guest.h>
+#include <uapi/linux/psp-sev.h>
+
+#include <asm/svm.h>
+#include <asm/sev.h>
+
+#include "sevguest.h"
+
+#define DEVICE_NAME "sev-guest"
+#define AAD_LEN 48
+#define MSG_HDR_VER 1
+
+struct snp_guest_crypto {
+ struct crypto_aead *tfm;
+ u8 *iv, *authtag;
+ int iv_len, a_len;
+};
+
+struct snp_guest_dev {
+ struct device *dev;
+ struct miscdevice misc;
+
+ struct snp_guest_crypto *crypto;
+ struct snp_guest_msg *request, *response;
+ struct snp_secrets_page_layout *layout;
+ struct snp_req_data input;
+ u32 *os_area_msg_seqno;
+ u8 *vmpck;
+};
+
+static u32 vmpck_id;
+module_param(vmpck_id, uint, 0444);
+MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
+
+/* Mutex to serialize the shared buffer access and command handling. */
+static DEFINE_MUTEX(snp_cmd_mutex);
+
+static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
+{
+ char zero_key[VMPCK_KEY_LEN] = {0};
+
+ if (snp_dev->vmpck)
+ return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
+
+ return true;
+}
+
+static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
+{
+ memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
+ snp_dev->vmpck = NULL;
+}
+
+static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ /* Read the current message sequence counter from secrets pages */
+ count = *snp_dev->os_area_msg_seqno;
+
+ return count + 1;
+}
+
+/* Return a non-zero on success */
+static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ u64 count = __snp_get_msg_seqno(snp_dev);
+
+ /*
+ * The message sequence counter for the SNP guest request is a 64-bit
+ * value but the version 2 of GHCB specification defines a 32-bit storage
+ * for it. If the counter exceeds the 32-bit value then return zero.
+ * The caller should check the return value, but if the caller happens to
+ * not check the value and use it, then the firmware treats zero as an
+ * invalid number and will fail the message request.
+ */
+ if (count >= UINT_MAX) {
+ dev_err(snp_dev->dev, "request message sequence counter overflow\n");
+ return 0;
+ }
+
+ return count;
+}
+
+static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
+{
+ /*
+ * The counter is also incremented by the PSP, so increment it by 2
+ * and save in secrets page.
+ */
+ *snp_dev->os_area_msg_seqno += 2;
+}
+
+static inline struct snp_guest_dev *to_snp_dev(struct file *file)
+{
+ struct miscdevice *dev = file->private_data;
+
+ return container_of(dev, struct snp_guest_dev, misc);
+}
+
+static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
+{
+ struct snp_guest_crypto *crypto;
+
+ crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
+ if (!crypto)
+ return NULL;
+
+ crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
+ if (IS_ERR(crypto->tfm))
+ goto e_free;
+
+ if (crypto_aead_setkey(crypto->tfm, key, keylen))
+ goto e_free_crypto;
+
+ crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
+ crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->iv)
+ goto e_free_crypto;
+
+ if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
+ if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
+ dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
+ goto e_free_iv;
+ }
+ }
+
+ crypto->a_len = crypto_aead_authsize(crypto->tfm);
+ crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
+ if (!crypto->authtag)
+ goto e_free_auth;
+
+ return crypto;
+
+e_free_auth:
+ kfree(crypto->authtag);
+e_free_iv:
+ kfree(crypto->iv);
+e_free_crypto:
+ crypto_free_aead(crypto->tfm);
+e_free:
+ kfree(crypto);
+
+ return NULL;
+}
+
+static void deinit_crypto(struct snp_guest_crypto *crypto)
+{
+ crypto_free_aead(crypto->tfm);
+ kfree(crypto->iv);
+ kfree(crypto->authtag);
+ kfree(crypto);
+}
+
+static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
+ u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
+{
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+ struct scatterlist src[3], dst[3];
+ DECLARE_CRYPTO_WAIT(wait);
+ struct aead_request *req;
+ int ret;
+
+ req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
+ if (!req)
+ return -ENOMEM;
+
+ /*
+ * AEAD memory operations:
+ * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
+ * | msg header | plaintext | hdr->authtag |
+ * | bytes 30h - 5Fh | or | |
+ * | | cipher | |
+ * +------------------+------------------+----------------+
+ */
+ sg_init_table(src, 3);
+ sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&src[1], src_buf, hdr->msg_sz);
+ sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
+
+ sg_init_table(dst, 3);
+ sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
+ sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
+ sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
+
+ aead_request_set_ad(req, AAD_LEN);
+ aead_request_set_tfm(req, crypto->tfm);
+ aead_request_set_callback(req, 0, crypto_req_done, &wait);
+
+ aead_request_set_crypt(req, src, dst, len, crypto->iv);
+ ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
+
+ aead_request_free(req);
+ return ret;
+}
+
+static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
+}
+
+static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
+ void *plaintext, size_t len)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg_hdr *hdr = &msg->hdr;
+
+ /* Build IV with response buffer sequence number */
+ memset(crypto->iv, 0, crypto->iv_len);
+ memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
+
+ return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
+}
+
+static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_guest_msg *resp = snp_dev->response;
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *req_hdr = &req->hdr;
+ struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
+
+ dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
+ resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
+
+ /* Verify that the sequence counter is incremented by 1 */
+ if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
+ return -EBADMSG;
+
+ /* Verify response message type and version number. */
+ if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
+ resp_hdr->msg_version != req_hdr->msg_version)
+ return -EBADMSG;
+
+ /*
+ * If the message size is greater than our buffer length then return
+ * an error.
+ */
+ if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
+ return -EBADMSG;
+
+ /* Decrypt the payload */
+ return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
+}
+
+static bool enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
+ void *payload, size_t sz)
+{
+ struct snp_guest_msg *req = snp_dev->request;
+ struct snp_guest_msg_hdr *hdr = &req->hdr;
+
+ memset(req, 0, sizeof(*req));
+
+ hdr->algo = SNP_AEAD_AES_256_GCM;
+ hdr->hdr_version = MSG_HDR_VER;
+ hdr->hdr_sz = sizeof(*hdr);
+ hdr->msg_type = type;
+ hdr->msg_version = version;
+ hdr->msg_seqno = seqno;
+ hdr->msg_vmpck = vmpck_id;
+ hdr->msg_sz = sz;
+
+ /* Verify the sequence number is non-zero */
+ if (!hdr->msg_seqno)
+ return -ENOSR;
+
+ dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
+ hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
+
+ return __enc_payload(snp_dev, req, payload, sz);
+}
+
+static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
+ u8 type, void *req_buf, size_t req_sz, void *resp_buf,
+ u32 resp_sz, __u64 *fw_err)
+{
+ unsigned long err;
+ u64 seqno;
+ int rc;
+
+ /* Get message sequence and verify that its a non-zero */
+ seqno = snp_get_msg_seqno(snp_dev);
+ if (!seqno)
+ return -EIO;
+
+ memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
+
+ /* Encrypt the userspace provided payload */
+ rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
+ if (rc)
+ return rc;
+
+ /* Call firmware to process the request */
+ rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
+ if (fw_err)
+ *fw_err = err;
+
+ if (rc)
+ return rc;
+
+ /*
+ * The verify_and_dec_payload() will fail only if the hypervisor is
+ * actively modifying the message header or corrupting the encrypted payload.
+ * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
+ * the key cannot be used for any communication. The key is disabled to ensure
+ * that AES-GCM does not use the same IV while encrypting the request payload.
+ */
+ rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
+ if (rc) {
+ dev_alert(snp_dev->dev,
+ "Detected unexpected decode failure, disabling the vmpck_id %d\n",
+ vmpck_id);
+ snp_disable_vmpck(snp_dev);
+ return rc;
+ }
+
+ /* Increment to new message sequence after payload decryption was successful. */
+ snp_inc_msg_seqno(snp_dev);
+
+ return 0;
+}
+
+static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
+{
+ struct snp_guest_crypto *crypto = snp_dev->crypto;
+ struct snp_report_resp *resp;
+ struct snp_report_req req;
+ int rc, resp_len;
+
+ lockdep_assert_held(&snp_cmd_mutex);
+
+ if (!arg->req_data || !arg->resp_data)
+ return -EINVAL;
+
+ if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
+ return -EFAULT;
+
+ /*
+ * The intermediate response buffer is used while decrypting the
+ * response payload. Make sure that it has enough space to cover the
+ * authtag.
+ */
+ resp_len = sizeof(resp->data) + crypto->a_len;
+ resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
+ if (!resp)
+ return -ENOMEM;
+
+ rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
+ SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
+ resp_len, &arg->fw_err);
+ if (rc)
+ goto e_free;
+
+ if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
+ rc = -EFAULT;
+
+e_free:
+ kfree(resp);
+ return rc;
+}
+
+static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
+{
+ struct snp_guest_dev *snp_dev = to_snp_dev(file);
+ void __user *argp = (void __user *)arg;
+ struct snp_guest_request_ioctl input;
+ int ret = -ENOTTY;
+
+ if (copy_from_user(&input, argp, sizeof(input)))
+ return -EFAULT;
+
+ input.fw_err = 0xff;
+
+ /* Message version must be non-zero */
+ if (!input.msg_version)
+ return -EINVAL;
+
+ mutex_lock(&snp_cmd_mutex);
+
+ /* Check if the VMPCK is not empty */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
+ mutex_unlock(&snp_cmd_mutex);
+ return -ENOTTY;
+ }
+
+ switch (ioctl) {
+ case SNP_GET_REPORT:
+ ret = get_report(snp_dev, &input);
+ break;
+ default:
+ break;
+ }
+
+ mutex_unlock(&snp_cmd_mutex);
+
+ if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
+ return -EFAULT;
+
+ return ret;
+}
+
+static void free_shared_pages(void *buf, size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ int ret;
+
+ if (!buf)
+ return;
+
+ ret = set_memory_encrypted((unsigned long)buf, npages);
+ if (ret) {
+ WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
+ return;
+ }
+
+ __free_pages(virt_to_page(buf), get_order(sz));
+}
+
+static void *alloc_shared_pages(size_t sz)
+{
+ unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
+ struct page *page;
+ int ret;
+
+ page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
+ if (IS_ERR(page))
+ return NULL;
+
+ ret = set_memory_decrypted((unsigned long)page_address(page), npages);
+ if (ret) {
+ pr_err("failed to mark page shared, ret=%d\n", ret);
+ __free_pages(page, get_order(sz));
+ return NULL;
+ }
+
+ return page_address(page);
+}
+
+static const struct file_operations snp_guest_fops = {
+ .owner = THIS_MODULE,
+ .unlocked_ioctl = snp_guest_ioctl,
+};
+
+static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
+{
+ u8 *key = NULL;
+
+ switch (id) {
+ case 0:
+ *seqno = &layout->os_area.msg_seqno_0;
+ key = layout->vmpck0;
+ break;
+ case 1:
+ *seqno = &layout->os_area.msg_seqno_1;
+ key = layout->vmpck1;
+ break;
+ case 2:
+ *seqno = &layout->os_area.msg_seqno_2;
+ key = layout->vmpck2;
+ break;
+ case 3:
+ *seqno = &layout->os_area.msg_seqno_3;
+ key = layout->vmpck3;
+ break;
+ default:
+ break;
+ }
+
+ return key;
+}
+
+static int __init snp_guest_probe(struct platform_device *pdev)
+{
+ struct snp_secrets_page_layout *layout;
+ struct snp_guest_platform_data *data;
+ struct device *dev = &pdev->dev;
+ struct snp_guest_dev *snp_dev;
+ struct miscdevice *misc;
+ int ret;
+
+ if (!dev->platform_data)
+ return -ENODEV;
+
+ data = (struct snp_guest_platform_data *)dev->platform_data;
+ layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
+ if (!layout)
+ return -ENODEV;
+
+ ret = -ENOMEM;
+ snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
+ if (!snp_dev)
+ goto e_unmap;
+
+ ret = -EINVAL;
+ snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
+ if (!snp_dev->vmpck) {
+ dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ /* Verify that VMPCK is not zero. */
+ if (is_vmpck_empty(snp_dev)) {
+ dev_err(dev, "vmpck id %d is null\n", vmpck_id);
+ goto e_unmap;
+ }
+
+ platform_set_drvdata(pdev, snp_dev);
+ snp_dev->dev = dev;
+ snp_dev->layout = layout;
+
+ /* Allocate the shared page used for the request and response message. */
+ snp_dev->request = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!snp_dev->request)
+ goto e_unmap;
+
+ snp_dev->response = alloc_shared_pages(sizeof(struct snp_guest_msg));
+ if (!snp_dev->response)
+ goto e_free_request;
+
+ ret = -EIO;
+ snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
+ if (!snp_dev->crypto)
+ goto e_free_response;
+
+ misc = &snp_dev->misc;
+ misc->minor = MISC_DYNAMIC_MINOR;
+ misc->name = DEVICE_NAME;
+ misc->fops = &snp_guest_fops;
+
+ /* initial the input address for guest request */
+ snp_dev->input.req_gpa = __pa(snp_dev->request);
+ snp_dev->input.resp_gpa = __pa(snp_dev->response);
+
+ ret = misc_register(misc);
+ if (ret)
+ goto e_free_response;
+
+ dev_info(dev, "Initialized SNP guest driver (using vmpck_id %d)\n", vmpck_id);
+ return 0;
+
+e_free_response:
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+e_free_request:
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+e_unmap:
+ iounmap(layout);
+ return ret;
+}
+
+static int __exit snp_guest_remove(struct platform_device *pdev)
+{
+ struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
+
+ free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
+ free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
+ deinit_crypto(snp_dev->crypto);
+ misc_deregister(&snp_dev->misc);
+
+ return 0;
+}
+
+static struct platform_driver snp_guest_driver = {
+ .remove = __exit_p(snp_guest_remove),
+ .driver = {
+ .name = "snp-guest",
+ },
+};
+
+module_platform_driver_probe(snp_guest_driver, snp_guest_probe);
+
+MODULE_AUTHOR("Brijesh Singh <[email protected]>");
+MODULE_LICENSE("GPL");
+MODULE_VERSION("1.0.0");
+MODULE_DESCRIPTION("AMD SNP Guest Driver");
diff --git a/drivers/virt/coco/sevguest/sevguest.h b/drivers/virt/coco/sevguest/sevguest.h
new file mode 100644
index 0000000..d39bdd0
--- /dev/null
+++ b/drivers/virt/coco/sevguest/sevguest.h
@@ -0,0 +1,98 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ *
+ * SEV-SNP API spec is available at https://developer.amd.com/sev
+ */
+
+#ifndef __VIRT_SEVGUEST_H__
+#define __VIRT_SEVGUEST_H__
+
+#include <linux/types.h>
+
+#define MAX_AUTHTAG_LEN 32
+
+/* See SNP spec SNP_GUEST_REQUEST section for the structure */
+enum msg_type {
+ SNP_MSG_TYPE_INVALID = 0,
+ SNP_MSG_CPUID_REQ,
+ SNP_MSG_CPUID_RSP,
+ SNP_MSG_KEY_REQ,
+ SNP_MSG_KEY_RSP,
+ SNP_MSG_REPORT_REQ,
+ SNP_MSG_REPORT_RSP,
+ SNP_MSG_EXPORT_REQ,
+ SNP_MSG_EXPORT_RSP,
+ SNP_MSG_IMPORT_REQ,
+ SNP_MSG_IMPORT_RSP,
+ SNP_MSG_ABSORB_REQ,
+ SNP_MSG_ABSORB_RSP,
+ SNP_MSG_VMRK_REQ,
+ SNP_MSG_VMRK_RSP,
+
+ SNP_MSG_TYPE_MAX
+};
+
+enum aead_algo {
+ SNP_AEAD_INVALID,
+ SNP_AEAD_AES_256_GCM,
+};
+
+struct snp_guest_msg_hdr {
+ u8 authtag[MAX_AUTHTAG_LEN];
+ u64 msg_seqno;
+ u8 rsvd1[8];
+ u8 algo;
+ u8 hdr_version;
+ u16 hdr_sz;
+ u8 msg_type;
+ u8 msg_version;
+ u16 msg_sz;
+ u32 rsvd2;
+ u8 msg_vmpck;
+ u8 rsvd3[35];
+} __packed;
+
+struct snp_guest_msg {
+ struct snp_guest_msg_hdr hdr;
+ u8 payload[4000];
+} __packed;
+
+/*
+ * The secrets page contains 96-bytes of reserved field that can be used by
+ * the guest OS. The guest OS uses the area to save the message sequence
+ * number for each VMPCK.
+ *
+ * See the GHCB spec section Secret page layout for the format for this area.
+ */
+struct secrets_os_area {
+ u32 msg_seqno_0;
+ u32 msg_seqno_1;
+ u32 msg_seqno_2;
+ u32 msg_seqno_3;
+ u64 ap_jump_table_pa;
+ u8 rsvd[40];
+ u8 guest_usage[32];
+} __packed;
+
+#define VMPCK_KEY_LEN 32
+
+/* See the SNP spec version 0.9 for secrets page format */
+struct snp_secrets_page_layout {
+ u32 version;
+ u32 imien : 1,
+ rsvd1 : 31;
+ u32 fms;
+ u32 rsvd2;
+ u8 gosvw[16];
+ u8 vmpck0[VMPCK_KEY_LEN];
+ u8 vmpck1[VMPCK_KEY_LEN];
+ u8 vmpck2[VMPCK_KEY_LEN];
+ u8 vmpck3[VMPCK_KEY_LEN];
+ struct secrets_os_area os_area;
+ u8 rsvd3[3840];
+} __packed;
+
+#endif /* __VIRT_SEVGUEST_H__ */
diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h
new file mode 100644
index 0000000..38f11d7
--- /dev/null
+++ b/include/uapi/linux/sev-guest.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
+/*
+ * Userspace interface for AMD SEV and SNP guest driver.
+ *
+ * Copyright (C) 2021 Advanced Micro Devices, Inc.
+ *
+ * Author: Brijesh Singh <[email protected]>
+ *
+ * SEV API specification is available at: https://developer.amd.com/sev/
+ */
+
+#ifndef __UAPI_LINUX_SEV_GUEST_H_
+#define __UAPI_LINUX_SEV_GUEST_H_
+
+#include <linux/types.h>
+
+struct snp_report_req {
+ /* user data that should be included in the report */
+ __u8 user_data[64];
+
+ /* The vmpl level to be included in the report */
+ __u32 vmpl;
+
+ /* Must be zero filled */
+ __u8 rsvd[28];
+};
+
+struct snp_report_resp {
+ /* response data, see SEV-SNP spec for the format */
+ __u8 data[4000];
+};
+
+struct snp_guest_request_ioctl {
+ /* message version number (must be non-zero) */
+ __u8 msg_version;
+
+ /* Request and response structure address */
+ __u64 req_data;
+ __u64 resp_data;
+
+ /* firmware error code on failure (see psp-sev.h) */
+ __u64 fw_err;
+};
+
+#define SNP_GUEST_REQ_IOC_TYPE 'S'
+
+/* Get SNP attestation report */
+#define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, struct snp_guest_request_ioctl)
+
+#endif /* __UAPI_LINUX_SEV_GUEST_H_ */
On Mon, Apr 18, 2022 at 12:40:11PM -0500, Tom Lendacky wrote:
> The driver name is used when registering the driver in
> snp_init_platform_device() and isn't really referenced after that. The
> module name is sevguest.ko, while the device name ends up being
> /dev/sev-guest.
>
> All that really matters is the device name that is exposed to user space.
> But if we want things to match, then, yes, we can change the name that is
> used in arch/x86/kernel/sev.c and drivers/virt/coco/sevguest/sevguest.c
> to "sev-guest" if that works. Do you want the module name to also be
> sev-guest.ko?
Just to ack this on the ML after our IRC discussion: yeah, let's keep
the common driver name sev-guest in order to avoid confusion. Other
functionality like SEV-ES or only SEV can still go in there, if needed,
but the name can remain.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
On Mon, Apr 18, 2022 at 09:42:31AM -0700, Dionna Amalie Glaze wrote:
> What is the intended name of this driver? I see the following
>
> +static struct platform_driver snp_guest_driver = {
> + .remove = __exit_p(snp_guest_remove),
> + .driver = {
> + .name = "snp-guest",
> + },
> +};
>
> yet...
>
> +#define DEVICE_NAME "sev-guest"
>
> and
>
> + misc->minor = MISC_DYNAMIC_MINOR;
> + misc->name = DEVICE_NAME;
> + misc->fops = &snp_guest_fops;
Gah, I have raised this in the past:
https://lore.kernel.org/r/[email protected]
but that aspect has veered off into the weeds.
I *think* this should be called "sev-guest".
Dov's driver which is mentioned in that thread, ended up being called
efi_secret so I guess sev-guest.
Tom?
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
What is the intended name of this driver? I see the following
+static struct platform_driver snp_guest_driver = {
+ .remove = __exit_p(snp_guest_remove),
+ .driver = {
+ .name = "snp-guest",
+ },
+};
yet...
+#define DEVICE_NAME "sev-guest"
and
+ misc->minor = MISC_DYNAMIC_MINOR;
+ misc->name = DEVICE_NAME;
+ misc->fops = &snp_guest_fops;
On Fri, Apr 8, 2022 at 2:14 AM tip-bot2 for Brijesh Singh
<[email protected]> wrote:
>
> The following commit has been merged into the x86/sev branch of tip:
>
> Commit-ID: fce96cf0443083e37455eff8f78fd240c621dae3
> Gitweb: https://git.kernel.org/tip/fce96cf0443083e37455eff8f78fd240c621dae3
> Author: Brijesh Singh <[email protected]>
> AuthorDate: Mon, 07 Mar 2022 15:33:53 -06:00
> Committer: Borislav Petkov <[email protected]>
> CommitterDate: Thu, 07 Apr 2022 16:47:12 +02:00
>
> virt: Add SEV-SNP guest driver
>
> The SEV-SNP specification provides the guest a mechanism to communicate
> with the PSP without risk from a malicious hypervisor who wishes to
> read, alter, drop or replay the messages sent. The driver uses
> snp_issue_guest_request() to issue GHCB SNP_GUEST_REQUEST or
> SNP_EXT_GUEST_REQUEST NAE events to submit the request to PSP.
>
> The PSP requires that all communication should be encrypted using key
> specified through a struct snp_guest_platform_data descriptor.
>
> Userspace can use SNP_GET_REPORT ioctl() to query the guest attestation
> report.
>
> See SEV-SNP spec section Guest Messages for more details.
>
> [ bp: Remove the "what" from the commit message, massage. ]
>
> Signed-off-by: Brijesh Singh <[email protected]>
> Signed-off-by: Borislav Petkov <[email protected]>
> Link: https://lore.kernel.org/r/[email protected]
> ---
> Documentation/virt/coco/sevguest.rst | 86 ++++-
> Documentation/virt/index.rst | 1 +-
> drivers/virt/Kconfig | 3 +-
> drivers/virt/Makefile | 1 +-
> drivers/virt/coco/sevguest/Kconfig | 14 +-
> drivers/virt/coco/sevguest/Makefile | 2 +-
> drivers/virt/coco/sevguest/sevguest.c | 607 +++++++++++++++++++++++++-
> drivers/virt/coco/sevguest/sevguest.h | 98 ++++-
> include/uapi/linux/sev-guest.h | 50 ++-
> 9 files changed, 862 insertions(+)
> create mode 100644 Documentation/virt/coco/sevguest.rst
> create mode 100644 drivers/virt/coco/sevguest/Kconfig
> create mode 100644 drivers/virt/coco/sevguest/Makefile
> create mode 100644 drivers/virt/coco/sevguest/sevguest.c
> create mode 100644 drivers/virt/coco/sevguest/sevguest.h
> create mode 100644 include/uapi/linux/sev-guest.h
>
> diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst
> new file mode 100644
> index 0000000..3da782e
> --- /dev/null
> +++ b/Documentation/virt/coco/sevguest.rst
> @@ -0,0 +1,86 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +===================================================================
> +The Definitive SEV Guest API Documentation
> +===================================================================
> +
> +1. General description
> +======================
> +
> +The SEV API is a set of ioctls that are used by the guest or hypervisor
> +to get or set a certain aspect of the SEV virtual machine. The ioctls belong
> +to the following classes:
> +
> + - Hypervisor ioctls: These query and set global attributes which affect the
> + whole SEV firmware. These ioctl are used by platform provisioning tools.
> +
> + - Guest ioctls: These query and set attributes of the SEV virtual machine.
> +
> +2. API description
> +==================
> +
> +This section describes ioctls that is used for querying the SEV guest report
> +from the SEV firmware. For each ioctl, the following information is provided
> +along with a description:
> +
> + Technology:
> + which SEV technology provides this ioctl. SEV, SEV-ES, SEV-SNP or all.
> +
> + Type:
> + hypervisor or guest. The ioctl can be used inside the guest or the
> + hypervisor.
> +
> + Parameters:
> + what parameters are accepted by the ioctl.
> +
> + Returns:
> + the return value. General error numbers (-ENOMEM, -EINVAL)
> + are not detailed, but errors with specific meanings are.
> +
> +The guest ioctl should be issued on a file descriptor of the /dev/sev-guest device.
> +The ioctl accepts struct snp_user_guest_request. The input and output structure is
> +specified through the req_data and resp_data field respectively. If the ioctl fails
> +to execute due to a firmware error, then fw_err code will be set otherwise the
> +fw_err will be set to 0x00000000000000ff.
> +
> +The firmware checks that the message sequence counter is one greater than
> +the guests message sequence counter. If guest driver fails to increment message
> +counter (e.g. counter overflow), then -EIO will be returned.
> +
> +::
> +
> + struct snp_guest_request_ioctl {
> + /* Message version number */
> + __u32 msg_version;
> +
> + /* Request and response structure address */
> + __u64 req_data;
> + __u64 resp_data;
> +
> + /* firmware error code on failure (see psp-sev.h) */
> + __u64 fw_err;
> + };
> +
> +2.1 SNP_GET_REPORT
> +------------------
> +
> +:Technology: sev-snp
> +:Type: guest ioctl
> +:Parameters (in): struct snp_report_req
> +:Returns (out): struct snp_report_resp on success, -negative on error
> +
> +The SNP_GET_REPORT ioctl can be used to query the attestation report from the
> +SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command
> +provided by the SEV-SNP firmware to query the attestation report.
> +
> +On success, the snp_report_resp.data will contains the report. The report
> +contain the format described in the SEV-SNP specification. See the SEV-SNP
> +specification for further details.
> +
> +
> +Reference
> +---------
> +
> +SEV-SNP and GHCB specification: developer.amd.com/sev
> +
> +The driver is based on SEV-SNP firmware spec 0.9 and GHCB spec version 2.0.
> diff --git a/Documentation/virt/index.rst b/Documentation/virt/index.rst
> index edea7fe..40ad0d2 100644
> --- a/Documentation/virt/index.rst
> +++ b/Documentation/virt/index.rst
> @@ -13,6 +13,7 @@ Linux Virtualization Support
> guest-halt-polling
> ne_overview
> acrn/index
> + coco/sevguest
>
> .. only:: html and subproject
>
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 121b929..7d3273c 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -47,4 +47,7 @@ source "drivers/virt/vboxguest/Kconfig"
> source "drivers/virt/nitro_enclaves/Kconfig"
>
> source "drivers/virt/acrn/Kconfig"
> +
> +source "drivers/virt/coco/sevguest/Kconfig"
> +
> endif
> diff --git a/drivers/virt/Makefile b/drivers/virt/Makefile
> index 108d0ff..7b87a7b 100644
> --- a/drivers/virt/Makefile
> +++ b/drivers/virt/Makefile
> @@ -9,3 +9,4 @@ obj-y += vboxguest/
>
> obj-$(CONFIG_NITRO_ENCLAVES) += nitro_enclaves/
> obj-$(CONFIG_ACRN_HSM) += acrn/
> +obj-$(CONFIG_SEV_GUEST) += coco/sevguest/
> diff --git a/drivers/virt/coco/sevguest/Kconfig b/drivers/virt/coco/sevguest/Kconfig
> new file mode 100644
> index 0000000..74ca1fe
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/Kconfig
> @@ -0,0 +1,14 @@
> +config SEV_GUEST
> + tristate "AMD SEV Guest driver"
> + default m
> + depends on AMD_MEM_ENCRYPT
> + select CRYPTO_AEAD2
> + select CRYPTO_GCM
> + help
> + SEV-SNP firmware provides the guest a mechanism to communicate with
> + the PSP without risk from a malicious hypervisor who wishes to read,
> + alter, drop or replay the messages sent. The driver provides
> + userspace interface to communicate with the PSP to request the
> + attestation report and more.
> +
> + If you choose 'M' here, this module will be called sevguest.
> diff --git a/drivers/virt/coco/sevguest/Makefile b/drivers/virt/coco/sevguest/Makefile
> new file mode 100644
> index 0000000..b1ffb2b
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/Makefile
> @@ -0,0 +1,2 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_SEV_GUEST) += sevguest.o
> diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c
> new file mode 100644
> index 0000000..beda93c
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/sevguest.c
> @@ -0,0 +1,607 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * AMD Secure Encrypted Virtualization Nested Paging (SEV-SNP) guest request interface
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <[email protected]>
> + */
> +
> +#define pr_fmt(fmt) "SNP: GUEST: " fmt
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/types.h>
> +#include <linux/mutex.h>
> +#include <linux/io.h>
> +#include <linux/platform_device.h>
> +#include <linux/miscdevice.h>
> +#include <linux/set_memory.h>
> +#include <linux/fs.h>
> +#include <crypto/aead.h>
> +#include <linux/scatterlist.h>
> +#include <linux/psp-sev.h>
> +#include <uapi/linux/sev-guest.h>
> +#include <uapi/linux/psp-sev.h>
> +
> +#include <asm/svm.h>
> +#include <asm/sev.h>
> +
> +#include "sevguest.h"
> +
> +#define DEVICE_NAME "sev-guest"
> +#define AAD_LEN 48
> +#define MSG_HDR_VER 1
> +
> +struct snp_guest_crypto {
> + struct crypto_aead *tfm;
> + u8 *iv, *authtag;
> + int iv_len, a_len;
> +};
> +
> +struct snp_guest_dev {
> + struct device *dev;
> + struct miscdevice misc;
> +
> + struct snp_guest_crypto *crypto;
> + struct snp_guest_msg *request, *response;
> + struct snp_secrets_page_layout *layout;
> + struct snp_req_data input;
> + u32 *os_area_msg_seqno;
> + u8 *vmpck;
> +};
> +
> +static u32 vmpck_id;
> +module_param(vmpck_id, uint, 0444);
> +MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
> +
> +/* Mutex to serialize the shared buffer access and command handling. */
> +static DEFINE_MUTEX(snp_cmd_mutex);
> +
> +static bool is_vmpck_empty(struct snp_guest_dev *snp_dev)
> +{
> + char zero_key[VMPCK_KEY_LEN] = {0};
> +
> + if (snp_dev->vmpck)
> + return !memcmp(snp_dev->vmpck, zero_key, VMPCK_KEY_LEN);
> +
> + return true;
> +}
> +
> +static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
> +{
> + memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
> + snp_dev->vmpck = NULL;
> +}
> +
> +static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + u64 count;
> +
> + lockdep_assert_held(&snp_cmd_mutex);
> +
> + /* Read the current message sequence counter from secrets pages */
> + count = *snp_dev->os_area_msg_seqno;
> +
> + return count + 1;
> +}
> +
> +/* Return a non-zero on success */
> +static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + u64 count = __snp_get_msg_seqno(snp_dev);
> +
> + /*
> + * The message sequence counter for the SNP guest request is a 64-bit
> + * value but the version 2 of GHCB specification defines a 32-bit storage
> + * for it. If the counter exceeds the 32-bit value then return zero.
> + * The caller should check the return value, but if the caller happens to
> + * not check the value and use it, then the firmware treats zero as an
> + * invalid number and will fail the message request.
> + */
> + if (count >= UINT_MAX) {
> + dev_err(snp_dev->dev, "request message sequence counter overflow\n");
> + return 0;
> + }
> +
> + return count;
> +}
> +
> +static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + /*
> + * The counter is also incremented by the PSP, so increment it by 2
> + * and save in secrets page.
> + */
> + *snp_dev->os_area_msg_seqno += 2;
> +}
> +
> +static inline struct snp_guest_dev *to_snp_dev(struct file *file)
> +{
> + struct miscdevice *dev = file->private_data;
> +
> + return container_of(dev, struct snp_guest_dev, misc);
> +}
> +
> +static struct snp_guest_crypto *init_crypto(struct snp_guest_dev *snp_dev, u8 *key, size_t keylen)
> +{
> + struct snp_guest_crypto *crypto;
> +
> + crypto = kzalloc(sizeof(*crypto), GFP_KERNEL_ACCOUNT);
> + if (!crypto)
> + return NULL;
> +
> + crypto->tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
> + if (IS_ERR(crypto->tfm))
> + goto e_free;
> +
> + if (crypto_aead_setkey(crypto->tfm, key, keylen))
> + goto e_free_crypto;
> +
> + crypto->iv_len = crypto_aead_ivsize(crypto->tfm);
> + crypto->iv = kmalloc(crypto->iv_len, GFP_KERNEL_ACCOUNT);
> + if (!crypto->iv)
> + goto e_free_crypto;
> +
> + if (crypto_aead_authsize(crypto->tfm) > MAX_AUTHTAG_LEN) {
> + if (crypto_aead_setauthsize(crypto->tfm, MAX_AUTHTAG_LEN)) {
> + dev_err(snp_dev->dev, "failed to set authsize to %d\n", MAX_AUTHTAG_LEN);
> + goto e_free_iv;
> + }
> + }
> +
> + crypto->a_len = crypto_aead_authsize(crypto->tfm);
> + crypto->authtag = kmalloc(crypto->a_len, GFP_KERNEL_ACCOUNT);
> + if (!crypto->authtag)
> + goto e_free_auth;
> +
> + return crypto;
> +
> +e_free_auth:
> + kfree(crypto->authtag);
> +e_free_iv:
> + kfree(crypto->iv);
> +e_free_crypto:
> + crypto_free_aead(crypto->tfm);
> +e_free:
> + kfree(crypto);
> +
> + return NULL;
> +}
> +
> +static void deinit_crypto(struct snp_guest_crypto *crypto)
> +{
> + crypto_free_aead(crypto->tfm);
> + kfree(crypto->iv);
> + kfree(crypto->authtag);
> + kfree(crypto);
> +}
> +
> +static int enc_dec_message(struct snp_guest_crypto *crypto, struct snp_guest_msg *msg,
> + u8 *src_buf, u8 *dst_buf, size_t len, bool enc)
> +{
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> + struct scatterlist src[3], dst[3];
> + DECLARE_CRYPTO_WAIT(wait);
> + struct aead_request *req;
> + int ret;
> +
> + req = aead_request_alloc(crypto->tfm, GFP_KERNEL);
> + if (!req)
> + return -ENOMEM;
> +
> + /*
> + * AEAD memory operations:
> + * +------ AAD -------+------- DATA -----+---- AUTHTAG----+
> + * | msg header | plaintext | hdr->authtag |
> + * | bytes 30h - 5Fh | or | |
> + * | | cipher | |
> + * +------------------+------------------+----------------+
> + */
> + sg_init_table(src, 3);
> + sg_set_buf(&src[0], &hdr->algo, AAD_LEN);
> + sg_set_buf(&src[1], src_buf, hdr->msg_sz);
> + sg_set_buf(&src[2], hdr->authtag, crypto->a_len);
> +
> + sg_init_table(dst, 3);
> + sg_set_buf(&dst[0], &hdr->algo, AAD_LEN);
> + sg_set_buf(&dst[1], dst_buf, hdr->msg_sz);
> + sg_set_buf(&dst[2], hdr->authtag, crypto->a_len);
> +
> + aead_request_set_ad(req, AAD_LEN);
> + aead_request_set_tfm(req, crypto->tfm);
> + aead_request_set_callback(req, 0, crypto_req_done, &wait);
> +
> + aead_request_set_crypt(req, src, dst, len, crypto->iv);
> + ret = crypto_wait_req(enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req), &wait);
> +
> + aead_request_free(req);
> + return ret;
> +}
> +
> +static int __enc_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> +
> + memset(crypto->iv, 0, crypto->iv_len);
> + memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> +
> + return enc_dec_message(crypto, msg, plaintext, msg->payload, len, true);
> +}
> +
> +static int dec_payload(struct snp_guest_dev *snp_dev, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> +
> + /* Build IV with response buffer sequence number */
> + memset(crypto->iv, 0, crypto->iv_len);
> + memcpy(crypto->iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> +
> + return enc_dec_message(crypto, msg, msg->payload, plaintext, len, false);
> +}
> +
> +static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_guest_msg *resp = snp_dev->response;
> + struct snp_guest_msg *req = snp_dev->request;
> + struct snp_guest_msg_hdr *req_hdr = &req->hdr;
> + struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
> +
> + dev_dbg(snp_dev->dev, "response [seqno %lld type %d version %d sz %d]\n",
> + resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version, resp_hdr->msg_sz);
> +
> + /* Verify that the sequence counter is incremented by 1 */
> + if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
> + return -EBADMSG;
> +
> + /* Verify response message type and version number. */
> + if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
> + resp_hdr->msg_version != req_hdr->msg_version)
> + return -EBADMSG;
> +
> + /*
> + * If the message size is greater than our buffer length then return
> + * an error.
> + */
> + if (unlikely((resp_hdr->msg_sz + crypto->a_len) > sz))
> + return -EBADMSG;
> +
> + /* Decrypt the payload */
> + return dec_payload(snp_dev, resp, payload, resp_hdr->msg_sz + crypto->a_len);
> +}
> +
> +static bool enc_payload(struct snp_guest_dev *snp_dev, u64 seqno, int version, u8 type,
> + void *payload, size_t sz)
> +{
> + struct snp_guest_msg *req = snp_dev->request;
> + struct snp_guest_msg_hdr *hdr = &req->hdr;
> +
> + memset(req, 0, sizeof(*req));
> +
> + hdr->algo = SNP_AEAD_AES_256_GCM;
> + hdr->hdr_version = MSG_HDR_VER;
> + hdr->hdr_sz = sizeof(*hdr);
> + hdr->msg_type = type;
> + hdr->msg_version = version;
> + hdr->msg_seqno = seqno;
> + hdr->msg_vmpck = vmpck_id;
> + hdr->msg_sz = sz;
> +
> + /* Verify the sequence number is non-zero */
> + if (!hdr->msg_seqno)
> + return -ENOSR;
> +
> + dev_dbg(snp_dev->dev, "request [seqno %lld type %d version %d sz %d]\n",
> + hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
> +
> + return __enc_payload(snp_dev, req, payload, sz);
> +}
> +
> +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> + u32 resp_sz, __u64 *fw_err)
> +{
> + unsigned long err;
> + u64 seqno;
> + int rc;
> +
> + /* Get message sequence and verify that its a non-zero */
> + seqno = snp_get_msg_seqno(snp_dev);
> + if (!seqno)
> + return -EIO;
> +
> + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
> +
> + /* Encrypt the userspace provided payload */
> + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
> + if (rc)
> + return rc;
> +
> + /* Call firmware to process the request */
> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> + if (fw_err)
> + *fw_err = err;
> +
> + if (rc)
> + return rc;
> +
> + /*
> + * The verify_and_dec_payload() will fail only if the hypervisor is
> + * actively modifying the message header or corrupting the encrypted payload.
> + * This hints that hypervisor is acting in a bad faith. Disable the VMPCK so that
> + * the key cannot be used for any communication. The key is disabled to ensure
> + * that AES-GCM does not use the same IV while encrypting the request payload.
> + */
> + rc = verify_and_dec_payload(snp_dev, resp_buf, resp_sz);
> + if (rc) {
> + dev_alert(snp_dev->dev,
> + "Detected unexpected decode failure, disabling the vmpck_id %d\n",
> + vmpck_id);
> + snp_disable_vmpck(snp_dev);
> + return rc;
> + }
> +
> + /* Increment to new message sequence after payload decryption was successful. */
> + snp_inc_msg_seqno(snp_dev);
> +
> + return 0;
> +}
> +
> +static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> +{
> + struct snp_guest_crypto *crypto = snp_dev->crypto;
> + struct snp_report_resp *resp;
> + struct snp_report_req req;
> + int rc, resp_len;
> +
> + lockdep_assert_held(&snp_cmd_mutex);
> +
> + if (!arg->req_data || !arg->resp_data)
> + return -EINVAL;
> +
> + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req)))
> + return -EFAULT;
> +
> + /*
> + * The intermediate response buffer is used while decrypting the
> + * response payload. Make sure that it has enough space to cover the
> + * authtag.
> + */
> + resp_len = sizeof(resp->data) + crypto->a_len;
> + resp = kzalloc(resp_len, GFP_KERNEL_ACCOUNT);
> + if (!resp)
> + return -ENOMEM;
> +
> + rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, arg->msg_version,
> + SNP_MSG_REPORT_REQ, &req, sizeof(req), resp->data,
> + resp_len, &arg->fw_err);
> + if (rc)
> + goto e_free;
> +
> + if (copy_to_user((void __user *)arg->resp_data, resp, sizeof(*resp)))
> + rc = -EFAULT;
> +
> +e_free:
> + kfree(resp);
> + return rc;
> +}
> +
> +static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
> +{
> + struct snp_guest_dev *snp_dev = to_snp_dev(file);
> + void __user *argp = (void __user *)arg;
> + struct snp_guest_request_ioctl input;
> + int ret = -ENOTTY;
> +
> + if (copy_from_user(&input, argp, sizeof(input)))
> + return -EFAULT;
> +
> + input.fw_err = 0xff;
> +
> + /* Message version must be non-zero */
> + if (!input.msg_version)
> + return -EINVAL;
> +
> + mutex_lock(&snp_cmd_mutex);
> +
> + /* Check if the VMPCK is not empty */
> + if (is_vmpck_empty(snp_dev)) {
> + dev_err_ratelimited(snp_dev->dev, "VMPCK is disabled\n");
> + mutex_unlock(&snp_cmd_mutex);
> + return -ENOTTY;
> + }
> +
> + switch (ioctl) {
> + case SNP_GET_REPORT:
> + ret = get_report(snp_dev, &input);
> + break;
> + default:
> + break;
> + }
> +
> + mutex_unlock(&snp_cmd_mutex);
> +
> + if (input.fw_err && copy_to_user(argp, &input, sizeof(input)))
> + return -EFAULT;
> +
> + return ret;
> +}
> +
> +static void free_shared_pages(void *buf, size_t sz)
> +{
> + unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> + int ret;
> +
> + if (!buf)
> + return;
> +
> + ret = set_memory_encrypted((unsigned long)buf, npages);
> + if (ret) {
> + WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
> + return;
> + }
> +
> + __free_pages(virt_to_page(buf), get_order(sz));
> +}
> +
> +static void *alloc_shared_pages(size_t sz)
> +{
> + unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> + struct page *page;
> + int ret;
> +
> + page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
> + if (IS_ERR(page))
> + return NULL;
> +
> + ret = set_memory_decrypted((unsigned long)page_address(page), npages);
> + if (ret) {
> + pr_err("failed to mark page shared, ret=%d\n", ret);
> + __free_pages(page, get_order(sz));
> + return NULL;
> + }
> +
> + return page_address(page);
> +}
> +
> +static const struct file_operations snp_guest_fops = {
> + .owner = THIS_MODULE,
> + .unlocked_ioctl = snp_guest_ioctl,
> +};
> +
> +static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno)
> +{
> + u8 *key = NULL;
> +
> + switch (id) {
> + case 0:
> + *seqno = &layout->os_area.msg_seqno_0;
> + key = layout->vmpck0;
> + break;
> + case 1:
> + *seqno = &layout->os_area.msg_seqno_1;
> + key = layout->vmpck1;
> + break;
> + case 2:
> + *seqno = &layout->os_area.msg_seqno_2;
> + key = layout->vmpck2;
> + break;
> + case 3:
> + *seqno = &layout->os_area.msg_seqno_3;
> + key = layout->vmpck3;
> + break;
> + default:
> + break;
> + }
> +
> + return key;
> +}
> +
> +static int __init snp_guest_probe(struct platform_device *pdev)
> +{
> + struct snp_secrets_page_layout *layout;
> + struct snp_guest_platform_data *data;
> + struct device *dev = &pdev->dev;
> + struct snp_guest_dev *snp_dev;
> + struct miscdevice *misc;
> + int ret;
> +
> + if (!dev->platform_data)
> + return -ENODEV;
> +
> + data = (struct snp_guest_platform_data *)dev->platform_data;
> + layout = (__force void *)ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
> + if (!layout)
> + return -ENODEV;
> +
> + ret = -ENOMEM;
> + snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
> + if (!snp_dev)
> + goto e_unmap;
> +
> + ret = -EINVAL;
> + snp_dev->vmpck = get_vmpck(vmpck_id, layout, &snp_dev->os_area_msg_seqno);
> + if (!snp_dev->vmpck) {
> + dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
> + goto e_unmap;
> + }
> +
> + /* Verify that VMPCK is not zero. */
> + if (is_vmpck_empty(snp_dev)) {
> + dev_err(dev, "vmpck id %d is null\n", vmpck_id);
> + goto e_unmap;
> + }
> +
> + platform_set_drvdata(pdev, snp_dev);
> + snp_dev->dev = dev;
> + snp_dev->layout = layout;
> +
> + /* Allocate the shared page used for the request and response message. */
> + snp_dev->request = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!snp_dev->request)
> + goto e_unmap;
> +
> + snp_dev->response = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!snp_dev->response)
> + goto e_free_request;
> +
> + ret = -EIO;
> + snp_dev->crypto = init_crypto(snp_dev, snp_dev->vmpck, VMPCK_KEY_LEN);
> + if (!snp_dev->crypto)
> + goto e_free_response;
> +
> + misc = &snp_dev->misc;
> + misc->minor = MISC_DYNAMIC_MINOR;
> + misc->name = DEVICE_NAME;
> + misc->fops = &snp_guest_fops;
> +
> + /* initial the input address for guest request */
> + snp_dev->input.req_gpa = __pa(snp_dev->request);
> + snp_dev->input.resp_gpa = __pa(snp_dev->response);
> +
> + ret = misc_register(misc);
> + if (ret)
> + goto e_free_response;
> +
> + dev_info(dev, "Initialized SNP guest driver (using vmpck_id %d)\n", vmpck_id);
> + return 0;
> +
> +e_free_response:
> + free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> +e_free_request:
> + free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> +e_unmap:
> + iounmap(layout);
> + return ret;
> +}
> +
> +static int __exit snp_guest_remove(struct platform_device *pdev)
> +{
> + struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
> +
> + free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> + free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> + deinit_crypto(snp_dev->crypto);
> + misc_deregister(&snp_dev->misc);
> +
> + return 0;
> +}
> +
> +static struct platform_driver snp_guest_driver = {
> + .remove = __exit_p(snp_guest_remove),
> + .driver = {
> + .name = "snp-guest",
> + },
> +};
> +
> +module_platform_driver_probe(snp_guest_driver, snp_guest_probe);
> +
> +MODULE_AUTHOR("Brijesh Singh <[email protected]>");
> +MODULE_LICENSE("GPL");
> +MODULE_VERSION("1.0.0");
> +MODULE_DESCRIPTION("AMD SNP Guest Driver");
> diff --git a/drivers/virt/coco/sevguest/sevguest.h b/drivers/virt/coco/sevguest/sevguest.h
> new file mode 100644
> index 0000000..d39bdd0
> --- /dev/null
> +++ b/drivers/virt/coco/sevguest/sevguest.h
> @@ -0,0 +1,98 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <[email protected]>
> + *
> + * SEV-SNP API spec is available at https://developer.amd.com/sev
> + */
> +
> +#ifndef __VIRT_SEVGUEST_H__
> +#define __VIRT_SEVGUEST_H__
> +
> +#include <linux/types.h>
> +
> +#define MAX_AUTHTAG_LEN 32
> +
> +/* See SNP spec SNP_GUEST_REQUEST section for the structure */
> +enum msg_type {
> + SNP_MSG_TYPE_INVALID = 0,
> + SNP_MSG_CPUID_REQ,
> + SNP_MSG_CPUID_RSP,
> + SNP_MSG_KEY_REQ,
> + SNP_MSG_KEY_RSP,
> + SNP_MSG_REPORT_REQ,
> + SNP_MSG_REPORT_RSP,
> + SNP_MSG_EXPORT_REQ,
> + SNP_MSG_EXPORT_RSP,
> + SNP_MSG_IMPORT_REQ,
> + SNP_MSG_IMPORT_RSP,
> + SNP_MSG_ABSORB_REQ,
> + SNP_MSG_ABSORB_RSP,
> + SNP_MSG_VMRK_REQ,
> + SNP_MSG_VMRK_RSP,
> +
> + SNP_MSG_TYPE_MAX
> +};
> +
> +enum aead_algo {
> + SNP_AEAD_INVALID,
> + SNP_AEAD_AES_256_GCM,
> +};
> +
> +struct snp_guest_msg_hdr {
> + u8 authtag[MAX_AUTHTAG_LEN];
> + u64 msg_seqno;
> + u8 rsvd1[8];
> + u8 algo;
> + u8 hdr_version;
> + u16 hdr_sz;
> + u8 msg_type;
> + u8 msg_version;
> + u16 msg_sz;
> + u32 rsvd2;
> + u8 msg_vmpck;
> + u8 rsvd3[35];
> +} __packed;
> +
> +struct snp_guest_msg {
> + struct snp_guest_msg_hdr hdr;
> + u8 payload[4000];
> +} __packed;
> +
> +/*
> + * The secrets page contains 96-bytes of reserved field that can be used by
> + * the guest OS. The guest OS uses the area to save the message sequence
> + * number for each VMPCK.
> + *
> + * See the GHCB spec section Secret page layout for the format for this area.
> + */
> +struct secrets_os_area {
> + u32 msg_seqno_0;
> + u32 msg_seqno_1;
> + u32 msg_seqno_2;
> + u32 msg_seqno_3;
> + u64 ap_jump_table_pa;
> + u8 rsvd[40];
> + u8 guest_usage[32];
> +} __packed;
> +
> +#define VMPCK_KEY_LEN 32
> +
> +/* See the SNP spec version 0.9 for secrets page format */
> +struct snp_secrets_page_layout {
> + u32 version;
> + u32 imien : 1,
> + rsvd1 : 31;
> + u32 fms;
> + u32 rsvd2;
> + u8 gosvw[16];
> + u8 vmpck0[VMPCK_KEY_LEN];
> + u8 vmpck1[VMPCK_KEY_LEN];
> + u8 vmpck2[VMPCK_KEY_LEN];
> + u8 vmpck3[VMPCK_KEY_LEN];
> + struct secrets_os_area os_area;
> + u8 rsvd3[3840];
> +} __packed;
> +
> +#endif /* __VIRT_SEVGUEST_H__ */
> diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h
> new file mode 100644
> index 0000000..38f11d7
> --- /dev/null
> +++ b/include/uapi/linux/sev-guest.h
> @@ -0,0 +1,50 @@
> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */
> +/*
> + * Userspace interface for AMD SEV and SNP guest driver.
> + *
> + * Copyright (C) 2021 Advanced Micro Devices, Inc.
> + *
> + * Author: Brijesh Singh <[email protected]>
> + *
> + * SEV API specification is available at: https://developer.amd.com/sev/
> + */
> +
> +#ifndef __UAPI_LINUX_SEV_GUEST_H_
> +#define __UAPI_LINUX_SEV_GUEST_H_
> +
> +#include <linux/types.h>
> +
> +struct snp_report_req {
> + /* user data that should be included in the report */
> + __u8 user_data[64];
> +
> + /* The vmpl level to be included in the report */
> + __u32 vmpl;
> +
> + /* Must be zero filled */
> + __u8 rsvd[28];
> +};
> +
> +struct snp_report_resp {
> + /* response data, see SEV-SNP spec for the format */
> + __u8 data[4000];
> +};
> +
> +struct snp_guest_request_ioctl {
> + /* message version number (must be non-zero) */
> + __u8 msg_version;
> +
> + /* Request and response structure address */
> + __u64 req_data;
> + __u64 resp_data;
> +
> + /* firmware error code on failure (see psp-sev.h) */
> + __u64 fw_err;
> +};
> +
> +#define SNP_GUEST_REQ_IOC_TYPE 'S'
> +
> +/* Get SNP attestation report */
> +#define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, struct snp_guest_request_ioctl)
> +
> +#endif /* __UAPI_LINUX_SEV_GUEST_H_ */
--
-Dionna Glaze, PhD (she/her)
On 4/18/22 12:14, Borislav Petkov wrote:
> On Mon, Apr 18, 2022 at 09:42:31AM -0700, Dionna Amalie Glaze wrote:
>> What is the intended name of this driver? I see the following
>>
>> +static struct platform_driver snp_guest_driver = {
>> + .remove = __exit_p(snp_guest_remove),
>> + .driver = {
>> + .name = "snp-guest",
>> + },
>> +};
>>
>> yet...
>>
>> +#define DEVICE_NAME "sev-guest"
>>
>> and
>>
>> + misc->minor = MISC_DYNAMIC_MINOR;
>> + misc->name = DEVICE_NAME;
>> + misc->fops = &snp_guest_fops;
>
> Gah, I have raised this in the past:
>
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Fr%2FYNxzJ2I3ZumTELLb%40zn.tnic&data=04%7C01%7Cthomas.lendacky%40amd.com%7Cb0af127a9aa44b85a23508da215ef064%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637858988899530603%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000&sdata=p7S%2BjZjFODp%2BSg2z2SKZIKLgyy80roI3UQpCZ2Dc2t0%3D&reserved=0
>
> but that aspect has veered off into the weeds.
>
> I *think* this should be called "sev-guest".
>
> Dov's driver which is mentioned in that thread, ended up being called
> efi_secret so I guess sev-guest.
>
> Tom?
The driver name is used when registering the driver in
snp_init_platform_device() and isn't really referenced after that. The
module name is sevguest.ko, while the device name ends up being
/dev/sev-guest.
All that really matters is the device name that is exposed to user space.
But if we want things to match, then, yes, we can change the name that is
used in arch/x86/kernel/sev.c and drivers/virt/coco/sevguest/sevguest.c
to "sev-guest" if that works. Do you want the module name to also be
sev-guest.ko?
Thanks,
Tom
>
Apologies for the necropost, but I noticed strange behavior testing my
own Golang-based wrapper around the /dev/sev-guest driver.
> +
> +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> + u32 resp_sz, __u64 *fw_err)
> +{
> + unsigned long err;
> + u64 seqno;
> + int rc;
> +
> + /* Get message sequence and verify that its a non-zero */
> + seqno = snp_get_msg_seqno(snp_dev);
> + if (!seqno)
> + return -EIO;
> +
> + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
> +
> + /* Encrypt the userspace provided payload */
> + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
> + if (rc)
> + return rc;
> +
> + /* Call firmware to process the request */
> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> + if (fw_err)
> + *fw_err = err;
> +
> + if (rc)
> + return rc;
> +
The fw_err is written back regardless of rc, so since err is
uninitialized, you can end up with garbage written back. I've worked
around this by only caring about fw_err when the result is -EIO, but
thought that I should bring this up.
--
-Dionna Glaze, PhD (she/her)
On Wed, Aug 24, 2022 at 12:01 PM Dionna Amalie Glaze
<[email protected]> wrote:
>
> Apologies for the necropost, but I noticed strange behavior testing my
> own Golang-based wrapper around the /dev/sev-guest driver.
>
> > +
> > +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> > + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> > + u32 resp_sz, __u64 *fw_err)
> > +{
> > + unsigned long err;
> > + u64 seqno;
> > + int rc;
> > +
> > + /* Get message sequence and verify that its a non-zero */
> > + seqno = snp_get_msg_seqno(snp_dev);
> > + if (!seqno)
> > + return -EIO;
> > +
> > + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
> > +
> > + /* Encrypt the userspace provided payload */
> > + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
> > + if (rc)
> > + return rc;
> > +
> > + /* Call firmware to process the request */
> > + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> > + if (fw_err)
> > + *fw_err = err;
> > +
> > + if (rc)
> > + return rc;
> > +
>
> The fw_err is written back regardless of rc, so since err is
> uninitialized, you can end up with garbage written back. I've worked
> around this by only caring about fw_err when the result is -EIO, but
> thought that I should bring this up.
I also noticed that we use a u64 in snp_guest_request_ioctl.fw_err and
u32 in sev_issue_cmd.error when these should be errors from the
sev_ret_code enum IIUC.
We can fix snp_issue_guest_request() to set |fw_err| to zero when it
returns 0 but what should we return to userspace if we encounter an
error that prevents the FW from even being called? In ` crypto: ccp -
Ensure psp_ret is always init'd in __sev_platform_init_locked()` we
set the return to -1 so we could continue that convection here and
better codify it in the sev_ret_code enum.
>
> --
> -Dionna Glaze, PhD (she/her)
On 8/24/22 14:28, Peter Gonda wrote:
> On Wed, Aug 24, 2022 at 12:01 PM Dionna Amalie Glaze
> <[email protected]> wrote:
>>
>> Apologies for the necropost, but I noticed strange behavior testing my
>> own Golang-based wrapper around the /dev/sev-guest driver.
>>
>>> +
>>> +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
>>> + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
>>> + u32 resp_sz, __u64 *fw_err)
>>> +{
>>> + unsigned long err;
>>> + u64 seqno;
>>> + int rc;
>>> +
>>> + /* Get message sequence and verify that its a non-zero */
>>> + seqno = snp_get_msg_seqno(snp_dev);
>>> + if (!seqno)
>>> + return -EIO;
>>> +
>>> + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
>>> +
>>> + /* Encrypt the userspace provided payload */
>>> + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
>>> + if (rc)
>>> + return rc;
>>> +
>>> + /* Call firmware to process the request */
>>> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
>>> + if (fw_err)
>>> + *fw_err = err;
>>> +
>>> + if (rc)
>>> + return rc;
>>> +
>>
>> The fw_err is written back regardless of rc, so since err is
>> uninitialized, you can end up with garbage written back. I've worked
>> around this by only caring about fw_err when the result is -EIO, but
>> thought that I should bring this up.
>
> I also noticed that we use a u64 in snp_guest_request_ioctl.fw_err and
> u32 in sev_issue_cmd.error when these should be errors from the
> sev_ret_code enum IIUC.
The reason for the u64 is that the Extended Guest Request can return a
firmware error or a hypervisor error. To distinguish between the two, a
firmware error is contained in the lower 32-bits, while a hypervisor error
is contained in the upper 32-bits (e.g. when not enough contiguous pages
of memory have been supplied).
Thanks,
Tom
>
> We can fix snp_issue_guest_request() to set |fw_err| to zero when it
> returns 0 but what should we return to userspace if we encounter an
> error that prevents the FW from even being called? In ` crypto: ccp -
> Ensure psp_ret is always init'd in __sev_platform_init_locked()` we
> set the return to -1 so we could continue that convection here and
> better codify it in the sev_ret_code enum.
>
>>
>> --
>> -Dionna Glaze, PhD (she/her)
On Thu, Aug 25, 2022 at 12:54 PM Tom Lendacky <[email protected]> wrote:
>
> On 8/24/22 14:28, Peter Gonda wrote:
> > On Wed, Aug 24, 2022 at 12:01 PM Dionna Amalie Glaze
> > <[email protected]> wrote:
> >>
> >> Apologies for the necropost, but I noticed strange behavior testing my
> >> own Golang-based wrapper around the /dev/sev-guest driver.
> >>
> >>> +
> >>> +static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, int msg_ver,
> >>> + u8 type, void *req_buf, size_t req_sz, void *resp_buf,
> >>> + u32 resp_sz, __u64 *fw_err)
> >>> +{
> >>> + unsigned long err;
> >>> + u64 seqno;
> >>> + int rc;
> >>> +
> >>> + /* Get message sequence and verify that its a non-zero */
> >>> + seqno = snp_get_msg_seqno(snp_dev);
> >>> + if (!seqno)
> >>> + return -EIO;
> >>> +
> >>> + memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
> >>> +
> >>> + /* Encrypt the userspace provided payload */
> >>> + rc = enc_payload(snp_dev, seqno, msg_ver, type, req_buf, req_sz);
> >>> + if (rc)
> >>> + return rc;
> >>> +
> >>> + /* Call firmware to process the request */
> >>> + rc = snp_issue_guest_request(exit_code, &snp_dev->input, &err);
> >>> + if (fw_err)
> >>> + *fw_err = err;
> >>> +
> >>> + if (rc)
> >>> + return rc;
> >>> +
> >>
> >> The fw_err is written back regardless of rc, so since err is
> >> uninitialized, you can end up with garbage written back. I've worked
> >> around this by only caring about fw_err when the result is -EIO, but
> >> thought that I should bring this up.
> >
> > I also noticed that we use a u64 in snp_guest_request_ioctl.fw_err and
> > u32 in sev_issue_cmd.error when these should be errors from the
> > sev_ret_code enum IIUC.
>
> The reason for the u64 is that the Extended Guest Request can return a
> firmware error or a hypervisor error. To distinguish between the two, a
> firmware error is contained in the lower 32-bits, while a hypervisor error
> is contained in the upper 32-bits (e.g. when not enough contiguous pages
> of memory have been supplied).
Ah, makes sense. I was trying to think of a way to codify the state
described above where we error so early in the IOCTL or call that the
PSP is never called, something like below. I think using UINT32_MAX
still works with how u64 of Extended Guest Request is spec'd. Is this
interesting to clean up the PSP driver and internal calls, and the new
sev-guest driver?
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 63dc626627a0..d1e605567d5e 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -22,6 +22,7 @@
#include <linux/efi.h>
#include <linux/platform_device.h>
#include <linux/io.h>
+#include <linux/psp-sev.h>
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -2177,6 +2178,8 @@ int snp_issue_guest_request(u64 exit_code,
struct snp_req_data *input, unsigned
if (!fw_err)
return -EINVAL;
+ fw_err = SEV_RET_NO_FW_CALL;
+
/*
* __sev_get_ghcb() needs to run with IRQs disabled because it is using
* a per-CPU GHCB.
@@ -2209,6 +2212,8 @@ int snp_issue_guest_request(u64 exit_code,
struct snp_req_data *input, unsigned
*fw_err = ghcb->save.sw_exit_info_2;
ret = -EIO;
+ } else {
+ *fw_err = 0;
}
e_put:
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9f588c9728f8..e71d6e39aa2b 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -439,7 +439,7 @@ static int __sev_platform_init_locked(int *error)
{
struct psp_device *psp = psp_master;
struct sev_device *sev;
- int rc, psp_ret = -1;
+ int rc, psp_ret = SEV_RET_NO_FW_CALL;
int (*init_function)(int *error);
if (!psp || !psp->sev_data)
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index 91b4c63d5cbf..b8f2c129d63d 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -36,6 +36,11 @@ enum {
* SEV Firmware status code
*/
...skipping...
#include <asm/cpu_entry_area.h>
#include <asm/stacktrace.h>
@@ -2177,6 +2178,8 @@ int snp_issue_guest_request(u64 exit_code,
struct snp_req_data *input, unsigned
if (!fw_err)
return -EINVAL;
+ fw_err = SEV_RET_NO_FW_CALL;
+
/*
* __sev_get_ghcb() needs to run with IRQs disabled because it is using
* a per-CPU GHCB.
@@ -2209,6 +2212,8 @@ int snp_issue_guest_request(u64 exit_code,
struct snp_req_data *input, unsigned
*fw_err = ghcb->save.sw_exit_info_2;
ret = -EIO;
+ } else {
+ *fw_err = 0;
}
e_put:
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9f588c9728f8..e71d6e39aa2b 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -439,7 +439,7 @@ static int __sev_platform_init_locked(int *error)
{
struct psp_device *psp = psp_master;
struct sev_device *sev;
- int rc, psp_ret = -1;
+ int rc, psp_ret = SEV_RET_NO_FW_CALL;
int (*init_function)(int *error);
if (!psp || !psp->sev_data)
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index 91b4c63d5cbf..b8f2c129d63d 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -36,6 +36,11 @@ enum {
* SEV Firmware status code
*/
typedef enum {
+ /*
+ * This error code is not in the SEV spec but is added to convey that
+ * there was an error that prevented the SEV Firmware from being called.
+ */
+ SEV_RET_NO_FW_CALL = -1,
SEV_RET_SUCCESS = 0,
SEV_RET_INVALID_PLATFORM_STATE,
SEV_RET_INVALID_GUEST_STATE,
> >
> >>
> >> --
> >> -Dionna Glaze, PhD (she/her)