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From:   Michael Roth <michael.roth@amd.com>
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Subject: [PATCH RFC v9 48/51] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command
Date:   Sun, 11 Jun 2023 23:25:56 -0500
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From: Brijesh Singh <brijesh.singh@amd.com>

The SEV-SNP firmware provides the SNP_CONFIG command used to set the
system-wide configuration value for SNP guests. The information includes
the TCB version string to be reported in guest attestation reports.

Version 2 of the GHCB specification adds an NAE (SNP extended guest
request) that a guest can use to query the reports that include additional
certificates.

In both cases, userspace provided additional data is included in the
attestation reports. The userspace will use the SNP_SET_EXT_CONFIG
command to give the certificate blob and the reported TCB version string
at once. Note that the specification defines certificate blob with a
specific GUID format; the userspace is responsible for building the
proper certificate blob. The ioctl treats it an opaque blob.

While it is not defined in the spec, but let's add SNP_GET_EXT_CONFIG
command that can be used to obtain the data programmed through the
SNP_SET_EXT_CONFIG.

Co-developed-by: Alexey Kardashevskiy <aik@amd.com>
Signed-off-by: Alexey Kardashevskiy <aik@amd.com>
Co-developed-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
[mdr: squash in doc patch from Dionna]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 Documentation/virt/coco/sev-guest.rst |  27 ++++
 drivers/crypto/ccp/sev-dev.c          | 178 ++++++++++++++++++++++++++
 drivers/crypto/ccp/sev-dev.h          |   2 +
 include/linux/psp-sev.h               |  10 ++
 include/uapi/linux/psp-sev.h          |  17 +++
 5 files changed, 234 insertions(+)

diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
index 11ea67c944df..6cad4226c348 100644
--- a/Documentation/virt/coco/sev-guest.rst
+++ b/Documentation/virt/coco/sev-guest.rst
@@ -145,6 +145,33 @@ The SNP_PLATFORM_STATUS command is used to query the SNP platform status. The
 status includes API major, minor version and more. See the SEV-SNP
 specification for further details.
 
+2.5 SNP_SET_EXT_CONFIG
+----------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_data_snp_ext_config
+:Returns (out): 0 on success, -negative on error
+
+The SNP_SET_EXT_CONFIG is used to set the system-wide configuration such as
+reported TCB version in the attestation report. The command is similar to
+SNP_CONFIG command defined in the SEV-SNP spec. The main difference is the
+command also accepts an additional certificate blob defined in the GHCB
+specification.
+
+If the certs_address is zero, then the previous certificate blob will deleted.
+For more information on the certificate blob layout, see the GHCB spec
+(extended guest request message).
+
+2.6 SNP_GET_EXT_CONFIG
+----------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_data_snp_ext_config
+:Returns (out): 0 on success, -negative on error
+
+The SNP_GET_EXT_CONFIG is used to query the system-wide configuration set
+through the SNP_SET_EXT_CONFIG.
+
 3. SEV-SNP CPUID Enforcement
 ============================
 
diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index b8e8c4da4025..175c24163ba0 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -1491,6 +1491,10 @@ static int __sev_snp_shutdown_locked(int *error)
 	data.length = sizeof(data);
 	data.iommu_snp_shutdown = 1;
 
+	/* Free the memory used for caching the certificate data */
+	sev_snp_certs_put(sev->snp_certs);
+	sev->snp_certs = NULL;
+
 	wbinvd_on_all_cpus();
 
 retry:
@@ -1829,6 +1833,126 @@ static int sev_ioctl_snp_platform_status(struct sev_issue_cmd *argp)
 	return ret;
 }
 
+static int sev_ioctl_snp_get_config(struct sev_issue_cmd *argp)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_user_data_ext_snp_config input;
+	struct sev_snp_certs *snp_certs;
+	int ret;
+
+	if (!sev->snp_initialized || !argp->data)
+		return -EINVAL;
+
+	memset(&input, 0, sizeof(input));
+
+	if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
+		return -EFAULT;
+
+	/* Copy the TCB version programmed through the SET_CONFIG to userspace */
+	if (input.config_address) {
+		if (copy_to_user((void * __user)input.config_address,
+				 &sev->snp_config, sizeof(struct sev_user_data_snp_config)))
+			return -EFAULT;
+	}
+
+	snp_certs = sev_snp_certs_get(sev->snp_certs);
+
+	/* Copy the extended certs programmed through the SNP_SET_CONFIG */
+	if (input.certs_address && snp_certs) {
+		if (input.certs_len < snp_certs->len) {
+			/* Return the certs length to userspace */
+			input.certs_len = snp_certs->len;
+
+			ret = -EIO;
+			goto e_done;
+		}
+
+		if (copy_to_user((void * __user)input.certs_address,
+				 snp_certs->data, snp_certs->len)) {
+			ret = -EFAULT;
+			goto put_exit;
+		}
+	}
+
+	ret = 0;
+
+e_done:
+	if (copy_to_user((void __user *)argp->data, &input, sizeof(input)))
+		ret = -EFAULT;
+
+put_exit:
+	sev_snp_certs_put(snp_certs);
+
+	return ret;
+}
+
+static int sev_ioctl_snp_set_config(struct sev_issue_cmd *argp, bool writable)
+{
+	struct sev_device *sev = psp_master->sev_data;
+	struct sev_user_data_ext_snp_config input;
+	struct sev_user_data_snp_config config;
+	struct sev_snp_certs *snp_certs = NULL;
+	void *certs = NULL;
+	int ret = 0;
+
+	if (!sev->snp_initialized || !argp->data)
+		return -EINVAL;
+
+	if (!writable)
+		return -EPERM;
+
+	memset(&input, 0, sizeof(input));
+
+	if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
+		return -EFAULT;
+
+	/* Copy the certs from userspace */
+	if (input.certs_address) {
+		if (!input.certs_len || !IS_ALIGNED(input.certs_len, PAGE_SIZE))
+			return -EINVAL;
+
+		certs = psp_copy_user_blob(input.certs_address, input.certs_len);
+		if (IS_ERR(certs))
+			return PTR_ERR(certs);
+	}
+
+	/* Issue the PSP command to update the TCB version using the SNP_CONFIG. */
+	if (input.config_address) {
+		memset(&config, 0, sizeof(config));
+		if (copy_from_user(&config,
+				   (void __user *)input.config_address, sizeof(config))) {
+			ret = -EFAULT;
+			goto e_free;
+		}
+
+		ret = __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error);
+		if (ret)
+			goto e_free;
+
+		memcpy(&sev->snp_config, &config, sizeof(config));
+	}
+
+	/*
+	 * If the new certs are passed then cache it else free the old certs.
+	 */
+	if (input.certs_len) {
+		snp_certs = sev_snp_certs_new(certs, input.certs_len);
+		if (!snp_certs) {
+			ret = -ENOMEM;
+			goto e_free;
+		}
+	}
+
+	sev_snp_certs_put(sev->snp_certs);
+	sev->snp_certs = snp_certs;
+
+	return 0;
+
+e_free:
+	kfree(certs);
+	return ret;
+}
+
 static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 {
 	void __user *argp = (void __user *)arg;
@@ -1883,6 +2007,12 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
 	case SNP_PLATFORM_STATUS:
 		ret = sev_ioctl_snp_platform_status(&input);
 		break;
+	case SNP_SET_EXT_CONFIG:
+		ret = sev_ioctl_snp_set_config(&input, writable);
+		break;
+	case SNP_GET_EXT_CONFIG:
+		ret = sev_ioctl_snp_get_config(&input);
+		break;
 	default:
 		ret = -EINVAL;
 		goto out;
@@ -1931,6 +2061,54 @@ int sev_guest_df_flush(int *error)
 }
 EXPORT_SYMBOL_GPL(sev_guest_df_flush);
 
+static void sev_snp_certs_release(struct kref *kref)
+{
+	struct sev_snp_certs *certs = container_of(kref, struct sev_snp_certs, kref);
+
+	kfree(certs->data);
+	kfree(certs);
+}
+
+struct sev_snp_certs *sev_snp_certs_new(void *data, u32 len)
+{
+	struct sev_snp_certs *certs;
+
+	if (!len || !data)
+		return NULL;
+
+	certs = kzalloc(sizeof(*certs), GFP_KERNEL);
+	if (!certs)
+		return NULL;
+
+	certs->data = data;
+	certs->len = len;
+	kref_init(&certs->kref);
+
+	return certs;
+}
+EXPORT_SYMBOL_GPL(sev_snp_certs_new);
+
+struct sev_snp_certs *sev_snp_certs_get(struct sev_snp_certs *certs)
+{
+	if (!certs)
+		return NULL;
+
+	if (!kref_get_unless_zero(&certs->kref))
+		return NULL;
+
+	return certs;
+}
+EXPORT_SYMBOL_GPL(sev_snp_certs_get);
+
+void sev_snp_certs_put(struct sev_snp_certs *certs)
+{
+	if (!certs)
+		return;
+
+	kref_put(&certs->kref, sev_snp_certs_release);
+}
+EXPORT_SYMBOL_GPL(sev_snp_certs_put);
+
 static void sev_exit(struct kref *ref)
 {
 	misc_deregister(&misc_dev->misc);
diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
index 19d79f9d4212..22374f3d3e2e 100644
--- a/drivers/crypto/ccp/sev-dev.h
+++ b/drivers/crypto/ccp/sev-dev.h
@@ -66,6 +66,8 @@ struct sev_device {
 
 	bool snp_initialized;
 	struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS];
+	struct sev_snp_certs *snp_certs;
+	struct sev_user_data_snp_config snp_config;
 };
 
 int sev_dev_init(struct psp_device *psp);
diff --git a/include/linux/psp-sev.h b/include/linux/psp-sev.h
index 5ae61de96e44..2191d8b5423a 100644
--- a/include/linux/psp-sev.h
+++ b/include/linux/psp-sev.h
@@ -24,6 +24,16 @@
 
 #define SEV_FW_BLOB_MAX_SIZE	0x4000	/* 16KB */
 
+struct sev_snp_certs {
+	void *data;
+	u32 len;
+	struct kref kref;
+};
+
+struct sev_snp_certs *sev_snp_certs_new(void *data, u32 len);
+struct sev_snp_certs *sev_snp_certs_get(struct sev_snp_certs *certs);
+void sev_snp_certs_put(struct sev_snp_certs *certs);
+
 /**
  * SEV platform state
  */
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index 4dc6a3e7b3d5..d1e6a0615546 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -29,6 +29,8 @@ enum {
 	SEV_GET_ID,	/* This command is deprecated, use SEV_GET_ID2 */
 	SEV_GET_ID2,
 	SNP_PLATFORM_STATUS,
+	SNP_SET_EXT_CONFIG,
+	SNP_GET_EXT_CONFIG,
 
 	SEV_MAX,
 };
@@ -201,6 +203,21 @@ struct sev_user_data_snp_config {
 	__u8 rsvd1[52];
 } __packed;
 
+/**
+ * struct sev_data_snp_ext_config - system wide configuration value for SNP.
+ *
+ * @config_address: address of the struct sev_user_data_snp_config or 0 when
+ *		reported_tcb does not need to be updated.
+ * @certs_address: address of extended guest request certificate chain or
+ *              0 when previous certificate should be removed on SNP_SET_EXT_CONFIG.
+ * @certs_len: length of the certs
+ */
+struct sev_user_data_ext_snp_config {
+	__u64 config_address;		/* In */
+	__u64 certs_address;		/* In */
+	__u32 certs_len;		/* In */
+};
+
 /**
  * struct sev_issue_cmd - SEV ioctl parameters
  *
-- 
2.25.1