When an SVSM is present, the guest can also request attestation reports
from the SVSM. These SVSM attestation reports can be used to attest the
SVSM and any services running within the SVSM.
Extend the config-fs attestation support to allow for an SVSM attestation
report. This involves creating four (4) new config-fs attributes:
- 'service-provider' (input)
This attribute is used to determine whether the attestation request
should be sent to the specified service provider or to the SEV
firmware. The SVSM service provider is represented by the value
'svsm'.
- 'service_guid' (input)
Used for requesting the attestation of a single service within the
service provider. A null GUID implies that the SVSM_ATTEST_SERVICES
call should be used to request the attestation report. A non-null
GUID implies that the SVSM_ATTEST_SINGLE_SERVICE call should be used.
- 'service_manifest_version' (input)
Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
represents a specific service manifest version be used for the
attestation report.
- 'manifestblob' (output)
Used to return the service manifest associated with the attestation
report.
Signed-off-by: Tom Lendacky <[email protected]>
---
Documentation/ABI/testing/configfs-tsm | 69 +++++++++++
arch/x86/include/asm/sev.h | 31 ++++-
arch/x86/kernel/sev.c | 50 ++++++++
drivers/virt/coco/sev-guest/sev-guest.c | 151 ++++++++++++++++++++++++
drivers/virt/coco/tsm.c | 93 ++++++++++++++-
include/linux/tsm.h | 11 ++
6 files changed, 402 insertions(+), 3 deletions(-)
diff --git a/Documentation/ABI/testing/configfs-tsm b/Documentation/ABI/testing/configfs-tsm
index dd24202b5ba5..72a7acdb5258 100644
--- a/Documentation/ABI/testing/configfs-tsm
+++ b/Documentation/ABI/testing/configfs-tsm
@@ -31,6 +31,21 @@ Description:
Standardization v2.03 Section 4.1.8.1 MSG_REPORT_REQ.
https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf
+What: /sys/kernel/config/tsm/report/$name/manifestblob
+Date: January, 2024
+KernelVersion: v6.10
+Contact: [email protected]
+Description:
+ (RO) Optional supplemental data that a TSM may emit, visibility
+ of this attribute depends on TSM, and may be empty if no
+ manifest data is available.
+
+ When @provider is "sev_guest" and the @service_provider is
+ "svsm" this file contains the service manifest used for the SVSM
+ attestation report from the Secure VM Service Module for SEV-SNP
+ Guests v1.00 Section 7.
+ https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
+
What: /sys/kernel/config/tsm/report/$name/provider
Date: September, 2023
KernelVersion: v6.7
@@ -80,3 +95,57 @@ Contact: [email protected]
Description:
(RO) Indicates the minimum permissible value that can be written
to @privlevel.
+
+What: /sys/kernel/config/tsm/report/$name/service_provider
+Date: January, 2024
+KernelVersion: v6.10
+Contact: [email protected]
+Description:
+ (WO) Attribute is visible if a TSM implementation provider
+ supports the concept of attestation reports from a service
+ provider for TVMs, like SEV-SNP running under an SVSM.
+ Specifying the service provider via this attribute will create
+ an attestation report as specified by the service provider.
+ Currently supported service-providers are:
+ svsm
+
+ For the SVSM service provider, see the Secure VM Service Module
+ for SEV-SNP Guests v1.00 Section 7.
+ https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
+
+What: /sys/kernel/config/tsm/report/$name/service_guid
+Date: January, 2024
+KernelVersion: v6.10
+Contact: [email protected]
+Description:
+ (WO) Attribute is visible if a TSM implementation provider
+ supports the concept of attestation reports from a service
+ provider for TVMs, like SEV-SNP running under an SVSM.
+ Specifying an empty/null GUID (00000000-0000-0000-0000-000000)
+ requests all active services within the service provider be
+ part of the attestation report. Specifying a GUID request
+ an attestation report of just the specified service using the
+ manifest form specified by the service_manifest_version
+ attribute.
+
+ For the SVSM service provider, see the Secure VM Service Module
+ for SEV-SNP Guests v1.00 Section 7.
+ https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
+
+What: /sys/kernel/config/tsm/report/$name/service_manifest_version
+Date: January, 2024
+KernelVersion: v6.10
+Contact: [email protected]
+Description:
+ (WO) Attribute is visible if a TSM implementation provider
+ supports the concept of attestation reports from a service
+ provider for TVMs, like SEV-SNP running under an SVSM.
+ Indicates the service manifest version requested for the
+ attestation report. If this field is not set by the user,
+ the default manifest version of the service (the service's
+ initial/first manifest version) is returned. The initial
+ manifest version is always available.
+
+ For the SVSM service provider, see the Secure VM Service Module
+ for SEV-SNP Guests v1.00 Section 7.
+ https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
index 066eb0ba3d63..94af7fb7a8e1 100644
--- a/arch/x86/include/asm/sev.h
+++ b/arch/x86/include/asm/sev.h
@@ -209,6 +209,27 @@ struct svsm_pvalidate_call {
struct svsm_pvalidate_entry entry[];
};
+/*
+ * The SVSM Attestation related structures
+ */
+struct svsm_location_entry {
+ u64 pa;
+ u32 len;
+ u8 rsvd[4];
+};
+
+struct svsm_attestation_call {
+ struct svsm_location_entry report_buffer;
+ struct svsm_location_entry nonce;
+ struct svsm_location_entry manifest_buffer;
+ struct svsm_location_entry certificates_buffer;
+
+ /* For attesting a single service */
+ u8 service_guid[16];
+ u32 service_manifest_version;
+ u8 rsvd[4];
+};
+
/*
* SVSM protocol structure
*/
@@ -232,6 +253,10 @@ struct svsm_call {
#define SVSM_CORE_CREATE_VCPU 2
#define SVSM_CORE_DELETE_VCPU 3
+#define SVSM_ATTEST_CALL(x) ((1ULL << 32) | (x))
+#define SVSM_ATTEST_SERVICES 0
+#define SVSM_ATTEST_SINGLE_SERVICE 1
+
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern void __sev_es_ist_enter(struct pt_regs *regs);
extern void __sev_es_ist_exit(void);
@@ -302,6 +327,7 @@ void snp_set_wakeup_secondary_cpu(void);
bool snp_init(struct boot_params *bp);
void __noreturn snp_abort(void);
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
+int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input);
void snp_accept_memory(phys_addr_t start, phys_addr_t end);
u64 snp_get_unsupported_features(u64 status);
u64 sev_get_status(void);
@@ -333,7 +359,10 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
{
return -ENOTTY;
}
-
+static inline int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input)
+{
+ return -ENOTTY;
+}
static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
static inline u64 sev_get_status(void) { return 0; }
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 7e2b9934a95d..0a06632898c6 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -2400,6 +2400,56 @@ static int __init init_sev_config(char *str)
}
__setup("sev=", init_sev_config);
+static void update_attestation_input(struct svsm_call *call, struct svsm_attestation_call *input)
+{
+ /* If (new) lengths have been returned, propograte them up */
+ if (call->rcx_out != call->rcx)
+ input->manifest_buffer.len = call->rcx_out;
+
+ if (call->rdx_out != call->rdx)
+ input->certificates_buffer.len = call->rdx_out;
+
+ if (call->r8_out != call->r8)
+ input->report_buffer.len = call->r8_out;
+}
+
+int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input)
+{
+ struct svsm_attestation_call *attest_call;
+ struct svsm_call call = {};
+ unsigned long flags;
+ u64 attest_call_pa;
+ int ret;
+
+ if (!vmpl)
+ return -EINVAL;
+
+ local_irq_save(flags);
+
+ call.caa = __svsm_get_caa();
+
+ attest_call = (struct svsm_attestation_call *)call.caa->svsm_buffer;
+ attest_call_pa = __svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
+
+ *attest_call = *input;
+
+ /*
+ * Set input registers for the request and set RDX and R8 to known
+ * values in order to detect length values being returned in them.
+ */
+ call.rax = call_id;
+ call.rcx = attest_call_pa;
+ call.rdx = -1;
+ call.r8 = -1;
+ ret = svsm_protocol(&call);
+ update_attestation_input(&call, input);
+
+ local_irq_restore(flags);
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(snp_issue_svsm_attestation_request);
+
int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
{
struct ghcb_state state;
diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
index bba6531cb606..0d2c9926a97c 100644
--- a/drivers/virt/coco/sev-guest/sev-guest.c
+++ b/drivers/virt/coco/sev-guest/sev-guest.c
@@ -38,6 +38,8 @@
#define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
#define SNP_REQ_RETRY_DELAY (2*HZ)
+#define SVSM_MAX_RETRIES 3
+
struct snp_guest_crypto {
struct crypto_aead *tfm;
u8 *iv, *authtag;
@@ -783,6 +785,148 @@ struct snp_msg_cert_entry {
u32 length;
};
+static int sev_svsm_report_new(struct tsm_report *report, void *data)
+{
+ unsigned int report_len, manifest_len, certificates_len;
+ void *report_blob, *manifest_blob, *certificates_blob;
+ struct svsm_attestation_call attest_call = {};
+ struct tsm_desc *desc = &report->desc;
+ unsigned int retry_count;
+ unsigned int size;
+ bool try_again;
+ void *buffer;
+ u64 call_id;
+ int ret;
+
+ /*
+ * Allocate pages for the request:
+ * - Report blob (4K)
+ * - Manifest blob (4K)
+ * - Certificate blob (16K)
+ *
+ * Above addresses must be 4K aligned
+ */
+ report_len = SZ_4K;
+ manifest_len = SZ_4K;
+ certificates_len = SEV_FW_BLOB_MAX_SIZE;
+
+ if (guid_is_null(&desc->service_guid)) {
+ call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SERVICES);
+ } else {
+ export_guid(attest_call.service_guid, &desc->service_guid);
+ attest_call.service_manifest_version = desc->service_manifest_version;
+
+ call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SINGLE_SERVICE);
+ }
+
+ retry_count = 0;
+
+retry:
+ size = report_len + manifest_len + certificates_len;
+ buffer = alloc_pages_exact(size, __GFP_ZERO);
+ if (!buffer)
+ return -ENOMEM;
+
+ report_blob = buffer;
+ attest_call.report_buffer.pa = __pa(report_blob);
+ attest_call.report_buffer.len = report_len;
+
+ manifest_blob = report_blob + report_len;
+ attest_call.manifest_buffer.pa = __pa(manifest_blob);
+ attest_call.manifest_buffer.len = manifest_len;
+
+ certificates_blob = manifest_blob + manifest_len;
+ attest_call.certificates_buffer.pa = __pa(certificates_blob);
+ attest_call.certificates_buffer.len = certificates_len;
+
+ attest_call.nonce.pa = __pa(desc->inblob);
+ attest_call.nonce.len = desc->inblob_len;
+
+ ret = snp_issue_svsm_attestation_request(call_id, &attest_call);
+ switch (ret) {
+ case SVSM_SUCCESS:
+ break;
+ case SVSM_ERR_INVALID_PARAMETER:
+ ret = -EINVAL;
+
+ if (retry_count >= SVSM_MAX_RETRIES)
+ goto error;
+
+ try_again = false;
+
+ if (attest_call.report_buffer.len > report_len) {
+ report_len = PAGE_ALIGN(attest_call.report_buffer.len);
+ try_again = true;
+ }
+
+ if (attest_call.manifest_buffer.len > manifest_len) {
+ manifest_len = PAGE_ALIGN(attest_call.manifest_buffer.len);
+ try_again = true;
+ }
+
+ if (attest_call.certificates_buffer.len > certificates_len) {
+ certificates_len = PAGE_ALIGN(attest_call.certificates_buffer.len);
+ try_again = true;
+ }
+
+ /* If one of the buffers wasn't large enough, retry the request */
+ if (try_again) {
+ free_pages_exact(buffer, size);
+ retry_count++;
+ goto retry;
+ }
+
+ goto error;
+ case SVSM_ERR_BUSY:
+ ret = -EAGAIN;
+ goto error;
+ default:
+ pr_err_ratelimited("SVSM attestation request failed (%#x)\n", ret);
+ ret = -EINVAL;
+ goto error;
+ }
+
+ ret = -ENOMEM;
+
+ report_len = attest_call.report_buffer.len;
+ void *rbuf __free(kvfree) = kvzalloc(report_len, GFP_KERNEL);
+ if (!rbuf)
+ goto error;
+
+ memcpy(rbuf, report_blob, report_len);
+ report->outblob = no_free_ptr(rbuf);
+ report->outblob_len = report_len;
+
+ manifest_len = attest_call.manifest_buffer.len;
+ void *mbuf __free(kvfree) = kvzalloc(manifest_len, GFP_KERNEL);
+ if (!mbuf)
+ goto error;
+
+ memcpy(mbuf, manifest_blob, manifest_len);
+ report->manifestblob = no_free_ptr(mbuf);
+ report->manifestblob_len = manifest_len;
+
+ certificates_len = attest_call.certificates_buffer.len;
+ if (!certificates_len)
+ goto success;
+
+ void *cbuf __free(kvfree) = kvzalloc(certificates_len, GFP_KERNEL);
+ if (!cbuf)
+ goto error;
+
+ memcpy(cbuf, certificates_blob, certificates_len);
+ report->auxblob = no_free_ptr(cbuf);
+ report->auxblob_len = certificates_len;
+
+success:
+ ret = 0;
+
+error:
+ free_pages_exact(buffer, size);
+
+ return ret;
+}
+
static int sev_report_new(struct tsm_report *report, void *data)
{
struct snp_msg_cert_entry *cert_table;
@@ -797,6 +941,13 @@ static int sev_report_new(struct tsm_report *report, void *data)
if (desc->inblob_len != SNP_REPORT_USER_DATA_SIZE)
return -EINVAL;
+ if (desc->service_provider) {
+ if (strcmp(desc->service_provider, "svsm"))
+ return -EINVAL;
+
+ return sev_svsm_report_new(report, data);
+ }
+
void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
if (!buf)
return -ENOMEM;
diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
index d1c2db83a8ca..46f230bf13ac 100644
--- a/drivers/virt/coco/tsm.c
+++ b/drivers/virt/coco/tsm.c
@@ -35,7 +35,7 @@ static DECLARE_RWSEM(tsm_rwsem);
* The attestation report format is TSM provider specific, when / if a standard
* materializes that can be published instead of the vendor layout. Until then
* the 'provider' attribute indicates the format of 'outblob', and optionally
- * 'auxblob'.
+ * 'auxblob' and 'manifestblob'.
*/
struct tsm_report_state {
@@ -48,6 +48,7 @@ struct tsm_report_state {
enum tsm_data_select {
TSM_REPORT,
TSM_CERTS,
+ TSM_MANIFEST,
};
static struct tsm_report *to_tsm_report(struct config_item *cfg)
@@ -119,6 +120,74 @@ static ssize_t tsm_report_privlevel_floor_show(struct config_item *cfg,
}
CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor);
+static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
+ const char *buf, size_t len)
+{
+ struct tsm_report *report = to_tsm_report(cfg);
+ size_t sp_len;
+ char *sp;
+ int rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+
+ sp_len = (buf[len - 1] != '\n') ? len : len - 1;
+
+ sp = kstrndup(buf, sp_len, GFP_KERNEL);
+ if (!sp)
+ return -ENOMEM;
+ kfree(report->desc.service_provider);
+
+ report->desc.service_provider = sp;
+
+ return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_provider);
+
+static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
+ const char *buf, size_t len)
+{
+ struct tsm_report *report = to_tsm_report(cfg);
+ int rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+
+ report->desc.service_guid = guid_null;
+
+ rc = guid_parse(buf, &report->desc.service_guid);
+ if (rc)
+ return rc;
+
+ return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_guid);
+
+static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
+ const char *buf, size_t len)
+{
+ struct tsm_report *report = to_tsm_report(cfg);
+ unsigned int val;
+ int rc;
+
+ rc = kstrtouint(buf, 0, &val);
+ if (rc)
+ return rc;
+
+ guard(rwsem_write)(&tsm_rwsem);
+ rc = try_advance_write_generation(report);
+ if (rc)
+ return rc;
+ report->desc.service_manifest_version = val;
+
+ return len;
+}
+CONFIGFS_ATTR_WO(tsm_report_, service_manifest_version);
+
static ssize_t tsm_report_inblob_write(struct config_item *cfg,
const void *buf, size_t count)
{
@@ -163,6 +232,9 @@ static ssize_t __read_report(struct tsm_report *report, void *buf, size_t count,
if (select == TSM_REPORT) {
out = report->outblob;
len = report->outblob_len;
+ } else if (select == TSM_MANIFEST) {
+ out = report->manifestblob;
+ len = report->manifestblob_len;
} else {
out = report->auxblob;
len = report->auxblob_len;
@@ -188,7 +260,7 @@ static ssize_t read_cached_report(struct tsm_report *report, void *buf,
/*
* A given TSM backend always fills in ->outblob regardless of
- * whether the report includes an auxblob or not.
+ * whether the report includes an auxblob/manifestblob or not.
*/
if (!report->outblob ||
state->read_generation != state->write_generation)
@@ -224,8 +296,10 @@ static ssize_t tsm_report_read(struct tsm_report *report, void *buf,
kvfree(report->outblob);
kvfree(report->auxblob);
+ kvfree(report->manifestblob);
report->outblob = NULL;
report->auxblob = NULL;
+ report->manifestblob = NULL;
rc = ops->report_new(report, provider.data);
if (rc < 0)
return rc;
@@ -252,6 +326,15 @@ static ssize_t tsm_report_auxblob_read(struct config_item *cfg, void *buf,
}
CONFIGFS_BIN_ATTR_RO(tsm_report_, auxblob, NULL, TSM_OUTBLOB_MAX);
+static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
+ size_t count)
+{
+ struct tsm_report *report = to_tsm_report(cfg);
+
+ return tsm_report_read(report, buf, count, TSM_MANIFEST);
+}
+CONFIGFS_BIN_ATTR_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX);
+
#define TSM_DEFAULT_ATTRS() \
&tsm_report_attr_generation, \
&tsm_report_attr_provider
@@ -265,6 +348,9 @@ static struct configfs_attribute *tsm_report_extra_attrs[] = {
TSM_DEFAULT_ATTRS(),
&tsm_report_attr_privlevel,
&tsm_report_attr_privlevel_floor,
+ &tsm_report_attr_service_provider,
+ &tsm_report_attr_service_guid,
+ &tsm_report_attr_service_manifest_version,
NULL,
};
@@ -280,6 +366,7 @@ static struct configfs_bin_attribute *tsm_report_bin_attrs[] = {
static struct configfs_bin_attribute *tsm_report_bin_extra_attrs[] = {
TSM_DEFAULT_BIN_ATTRS(),
&tsm_report_attr_auxblob,
+ &tsm_report_attr_manifestblob,
NULL,
};
@@ -288,8 +375,10 @@ static void tsm_report_item_release(struct config_item *cfg)
struct tsm_report *report = to_tsm_report(cfg);
struct tsm_report_state *state = to_state(report);
+ kvfree(report->manifestblob);
kvfree(report->auxblob);
kvfree(report->outblob);
+ kfree(report->desc.service_provider);
kfree(state);
}
diff --git a/include/linux/tsm.h b/include/linux/tsm.h
index 50c5769657d8..27cc97fe8dcd 100644
--- a/include/linux/tsm.h
+++ b/include/linux/tsm.h
@@ -4,6 +4,7 @@
#include <linux/sizes.h>
#include <linux/types.h>
+#include <linux/uuid.h>
#define TSM_INBLOB_MAX 64
#define TSM_OUTBLOB_MAX SZ_32K
@@ -19,11 +20,17 @@
* @privlevel: optional privilege level to associate with @outblob
* @inblob_len: sizeof @inblob
* @inblob: arbitrary input data
+ * @service_provider: optional name of where to obtain the tsm report blob
+ * @service_guid: optional service-provider service guid to attest
+ * @service_manifest_version: optional service-provider service manifest version requested
*/
struct tsm_desc {
unsigned int privlevel;
size_t inblob_len;
u8 inblob[TSM_INBLOB_MAX];
+ char *service_provider;
+ guid_t service_guid;
+ unsigned int service_manifest_version;
};
/**
@@ -33,6 +40,8 @@ struct tsm_desc {
* @outblob: generated evidence to provider to the attestation agent
* @auxblob_len: sizeof(@auxblob)
* @auxblob: (optional) auxiliary data to the report (e.g. certificate data)
+ * @manifestblob_len: sizeof(@manifestblob)
+ * @manifestblob: (optional) manifest data associated with the report
*/
struct tsm_report {
struct tsm_desc desc;
@@ -40,6 +49,8 @@ struct tsm_report {
u8 *outblob;
size_t auxblob_len;
u8 *auxblob;
+ size_t manifestblob_len;
+ u8 *manifestblob;
};
/**
--
2.43.2
Tom Lendacky wrote:
> When an SVSM is present, the guest can also request attestation reports
> from the SVSM. These SVSM attestation reports can be used to attest the
> SVSM and any services running within the SVSM.
>
> Extend the config-fs attestation support to allow for an SVSM attestation
> report. This involves creating four (4) new config-fs attributes:
>
> - 'service-provider' (input)
> This attribute is used to determine whether the attestation request
> should be sent to the specified service provider or to the SEV
> firmware. The SVSM service provider is represented by the value
> 'svsm'.
>
> - 'service_guid' (input)
> Used for requesting the attestation of a single service within the
> service provider. A null GUID implies that the SVSM_ATTEST_SERVICES
> call should be used to request the attestation report. A non-null
> GUID implies that the SVSM_ATTEST_SINGLE_SERVICE call should be used.
>
> - 'service_manifest_version' (input)
> Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
> represents a specific service manifest version be used for the
> attestation report.
>
> - 'manifestblob' (output)
> Used to return the service manifest associated with the attestation
> report.
>
> Signed-off-by: Tom Lendacky <[email protected]>
> ---
> Documentation/ABI/testing/configfs-tsm | 69 +++++++++++
> arch/x86/include/asm/sev.h | 31 ++++-
> arch/x86/kernel/sev.c | 50 ++++++++
> drivers/virt/coco/sev-guest/sev-guest.c | 151 ++++++++++++++++++++++++
> drivers/virt/coco/tsm.c | 93 ++++++++++++++-
> include/linux/tsm.h | 11 ++
> 6 files changed, 402 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/ABI/testing/configfs-tsm b/Documentation/ABI/testing/configfs-tsm
> index dd24202b5ba5..72a7acdb5258 100644
> --- a/Documentation/ABI/testing/configfs-tsm
> +++ b/Documentation/ABI/testing/configfs-tsm
> @@ -31,6 +31,21 @@ Description:
> Standardization v2.03 Section 4.1.8.1 MSG_REPORT_REQ.
> https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf
>
> +What: /sys/kernel/config/tsm/report/$name/manifestblob
> +Date: January, 2024
> +KernelVersion: v6.10
> +Contact: [email protected]
> +Description:
> + (RO) Optional supplemental data that a TSM may emit, visibility
> + of this attribute depends on TSM, and may be empty if no
> + manifest data is available.
> +
> + When @provider is "sev_guest" and the @service_provider is
> + "svsm" this file contains the service manifest used for the SVSM
> + attestation report from the Secure VM Service Module for SEV-SNP
> + Guests v1.00 Section 7.
> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
Should this be "See 'service_provider' for the format of this blob"? To
date external "format specification" links are only referenced once in
this file, and this one is now duplicated.
> +
> What: /sys/kernel/config/tsm/report/$name/provider
> Date: September, 2023
> KernelVersion: v6.7
> @@ -80,3 +95,57 @@ Contact: [email protected]
> Description:
> (RO) Indicates the minimum permissible value that can be written
> to @privlevel.
> +
> +What: /sys/kernel/config/tsm/report/$name/service_provider
> +Date: January, 2024
> +KernelVersion: v6.10
> +Contact: [email protected]
> +Description:
> + (WO) Attribute is visible if a TSM implementation provider
> + supports the concept of attestation reports from a service
> + provider for TVMs, like SEV-SNP running under an SVSM.
> + Specifying the service provider via this attribute will create
> + an attestation report as specified by the service provider.
> + Currently supported service-providers are:
> + svsm
> +
> + For the SVSM service provider, see the Secure VM Service Module
> + for SEV-SNP Guests v1.00 Section 7.
> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
Given "SVSM" is a cross vendor concept should this explicitly
callout: "For provider.service_provider == sev_guest.svsm" as
preparation for other implementations defining their "svsm" manifest
format?
> +
> +What: /sys/kernel/config/tsm/report/$name/service_guid
> +Date: January, 2024
> +KernelVersion: v6.10
> +Contact: [email protected]
> +Description:
> + (WO) Attribute is visible if a TSM implementation provider
> + supports the concept of attestation reports from a service
> + provider for TVMs, like SEV-SNP running under an SVSM.
> + Specifying an empty/null GUID (00000000-0000-0000-0000-000000)
> + requests all active services within the service provider be
> + part of the attestation report. Specifying a GUID request
> + an attestation report of just the specified service using the
> + manifest form specified by the service_manifest_version
> + attribute.
> +
> + For the SVSM service provider, see the Secure VM Service Module
> + for SEV-SNP Guests v1.00 Section 7.
> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
..another "See..." instead of duplicate.
> +
> +What: /sys/kernel/config/tsm/report/$name/service_manifest_version
> +Date: January, 2024
> +KernelVersion: v6.10
> +Contact: [email protected]
> +Description:
> + (WO) Attribute is visible if a TSM implementation provider
> + supports the concept of attestation reports from a service
> + provider for TVMs, like SEV-SNP running under an SVSM.
> + Indicates the service manifest version requested for the
> + attestation report. If this field is not set by the user,
> + the default manifest version of the service (the service's
> + initial/first manifest version) is returned. The initial
> + manifest version is always available.
..and that number is zero? Is there any expectation that the kernel
sanity checks this version, or how does the user figure out they need to
roll this request back?
> +
> + For the SVSM service provider, see the Secure VM Service Module
> + for SEV-SNP Guests v1.00 Section 7.
> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
Ditto on replacing this with a "See.." reference.
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index 066eb0ba3d63..94af7fb7a8e1 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -209,6 +209,27 @@ struct svsm_pvalidate_call {
> struct svsm_pvalidate_entry entry[];
> };
>
> +/*
> + * The SVSM Attestation related structures
> + */
> +struct svsm_location_entry {
> + u64 pa;
> + u32 len;
> + u8 rsvd[4];
> +};
> +
> +struct svsm_attestation_call {
> + struct svsm_location_entry report_buffer;
> + struct svsm_location_entry nonce;
> + struct svsm_location_entry manifest_buffer;
> + struct svsm_location_entry certificates_buffer;
> +
> + /* For attesting a single service */
> + u8 service_guid[16];
> + u32 service_manifest_version;
> + u8 rsvd[4];
> +};
> +
> /*
> * SVSM protocol structure
> */
> @@ -232,6 +253,10 @@ struct svsm_call {
> #define SVSM_CORE_CREATE_VCPU 2
> #define SVSM_CORE_DELETE_VCPU 3
>
> +#define SVSM_ATTEST_CALL(x) ((1ULL << 32) | (x))
> +#define SVSM_ATTEST_SERVICES 0
> +#define SVSM_ATTEST_SINGLE_SERVICE 1
> +
> #ifdef CONFIG_AMD_MEM_ENCRYPT
> extern void __sev_es_ist_enter(struct pt_regs *regs);
> extern void __sev_es_ist_exit(void);
> @@ -302,6 +327,7 @@ void snp_set_wakeup_secondary_cpu(void);
> bool snp_init(struct boot_params *bp);
> void __noreturn snp_abort(void);
> int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio);
> +int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input);
> void snp_accept_memory(phys_addr_t start, phys_addr_t end);
> u64 snp_get_unsupported_features(u64 status);
> u64 sev_get_status(void);
> @@ -333,7 +359,10 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in
> {
> return -ENOTTY;
> }
> -
> +static inline int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input)
> +{
> + return -ENOTTY;
> +}
> static inline void snp_accept_memory(phys_addr_t start, phys_addr_t end) { }
> static inline u64 snp_get_unsupported_features(u64 status) { return 0; }
> static inline u64 sev_get_status(void) { return 0; }
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 7e2b9934a95d..0a06632898c6 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -2400,6 +2400,56 @@ static int __init init_sev_config(char *str)
> }
> __setup("sev=", init_sev_config);
>
> +static void update_attestation_input(struct svsm_call *call, struct svsm_attestation_call *input)
> +{
> + /* If (new) lengths have been returned, propograte them up */
> + if (call->rcx_out != call->rcx)
> + input->manifest_buffer.len = call->rcx_out;
> +
> + if (call->rdx_out != call->rdx)
> + input->certificates_buffer.len = call->rdx_out;
> +
> + if (call->r8_out != call->r8)
> + input->report_buffer.len = call->r8_out;
> +}
> +
> +int snp_issue_svsm_attestation_request(u64 call_id, struct svsm_attestation_call *input)
> +{
> + struct svsm_attestation_call *attest_call;
> + struct svsm_call call = {};
> + unsigned long flags;
> + u64 attest_call_pa;
> + int ret;
> +
> + if (!vmpl)
> + return -EINVAL;
> +
> + local_irq_save(flags);
> +
> + call.caa = __svsm_get_caa();
> +
> + attest_call = (struct svsm_attestation_call *)call.caa->svsm_buffer;
> + attest_call_pa = __svsm_get_caa_pa() + offsetof(struct svsm_ca, svsm_buffer);
> +
> + *attest_call = *input;
> +
> + /*
> + * Set input registers for the request and set RDX and R8 to known
> + * values in order to detect length values being returned in them.
> + */
> + call.rax = call_id;
> + call.rcx = attest_call_pa;
> + call.rdx = -1;
> + call.r8 = -1;
> + ret = svsm_protocol(&call);
> + update_attestation_input(&call, input);
> +
> + local_irq_restore(flags);
> +
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(snp_issue_svsm_attestation_request);
> +
> int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, struct snp_guest_request_ioctl *rio)
> {
> struct ghcb_state state;
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index bba6531cb606..0d2c9926a97c 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -38,6 +38,8 @@
> #define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
> #define SNP_REQ_RETRY_DELAY (2*HZ)
>
> +#define SVSM_MAX_RETRIES 3
> +
> struct snp_guest_crypto {
> struct crypto_aead *tfm;
> u8 *iv, *authtag;
> @@ -783,6 +785,148 @@ struct snp_msg_cert_entry {
> u32 length;
> };
>
> +static int sev_svsm_report_new(struct tsm_report *report, void *data)
> +{
> + unsigned int report_len, manifest_len, certificates_len;
> + void *report_blob, *manifest_blob, *certificates_blob;
> + struct svsm_attestation_call attest_call = {};
> + struct tsm_desc *desc = &report->desc;
> + unsigned int retry_count;
> + unsigned int size;
> + bool try_again;
> + void *buffer;
> + u64 call_id;
> + int ret;
> +
> + /*
> + * Allocate pages for the request:
> + * - Report blob (4K)
> + * - Manifest blob (4K)
> + * - Certificate blob (16K)
> + *
> + * Above addresses must be 4K aligned
> + */
> + report_len = SZ_4K;
> + manifest_len = SZ_4K;
> + certificates_len = SEV_FW_BLOB_MAX_SIZE;
> +
> + if (guid_is_null(&desc->service_guid)) {
> + call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SERVICES);
> + } else {
> + export_guid(attest_call.service_guid, &desc->service_guid);
> + attest_call.service_manifest_version = desc->service_manifest_version;
> +
> + call_id = SVSM_ATTEST_CALL(SVSM_ATTEST_SINGLE_SERVICE);
> + }
> +
> + retry_count = 0;
> +
> +retry:
> + size = report_len + manifest_len + certificates_len;
> + buffer = alloc_pages_exact(size, __GFP_ZERO);
> + if (!buffer)
> + return -ENOMEM;
> +
> + report_blob = buffer;
> + attest_call.report_buffer.pa = __pa(report_blob);
> + attest_call.report_buffer.len = report_len;
> +
> + manifest_blob = report_blob + report_len;
> + attest_call.manifest_buffer.pa = __pa(manifest_blob);
> + attest_call.manifest_buffer.len = manifest_len;
> +
> + certificates_blob = manifest_blob + manifest_len;
> + attest_call.certificates_buffer.pa = __pa(certificates_blob);
> + attest_call.certificates_buffer.len = certificates_len;
> +
> + attest_call.nonce.pa = __pa(desc->inblob);
> + attest_call.nonce.len = desc->inblob_len;
> +
> + ret = snp_issue_svsm_attestation_request(call_id, &attest_call);
> + switch (ret) {
> + case SVSM_SUCCESS:
> + break;
> + case SVSM_ERR_INVALID_PARAMETER:
> + ret = -EINVAL;
> +
> + if (retry_count >= SVSM_MAX_RETRIES)
> + goto error;
> +
> + try_again = false;
> +
> + if (attest_call.report_buffer.len > report_len) {
> + report_len = PAGE_ALIGN(attest_call.report_buffer.len);
> + try_again = true;
> + }
> +
> + if (attest_call.manifest_buffer.len > manifest_len) {
> + manifest_len = PAGE_ALIGN(attest_call.manifest_buffer.len);
> + try_again = true;
> + }
> +
> + if (attest_call.certificates_buffer.len > certificates_len) {
> + certificates_len = PAGE_ALIGN(attest_call.certificates_buffer.len);
> + try_again = true;
> + }
> +
> + /* If one of the buffers wasn't large enough, retry the request */
> + if (try_again) {
> + free_pages_exact(buffer, size);
> + retry_count++;
> + goto retry;
> + }
> +
> + goto error;
> + case SVSM_ERR_BUSY:
> + ret = -EAGAIN;
> + goto error;
> + default:
> + pr_err_ratelimited("SVSM attestation request failed (%#x)\n", ret);
> + ret = -EINVAL;
> + goto error;
> + }
> +
> + ret = -ENOMEM;
> +
> + report_len = attest_call.report_buffer.len;
> + void *rbuf __free(kvfree) = kvzalloc(report_len, GFP_KERNEL);
> + if (!rbuf)
> + goto error;
> +
> + memcpy(rbuf, report_blob, report_len);
> + report->outblob = no_free_ptr(rbuf);
> + report->outblob_len = report_len;
> +
> + manifest_len = attest_call.manifest_buffer.len;
> + void *mbuf __free(kvfree) = kvzalloc(manifest_len, GFP_KERNEL);
> + if (!mbuf)
> + goto error;
> +
> + memcpy(mbuf, manifest_blob, manifest_len);
> + report->manifestblob = no_free_ptr(mbuf);
> + report->manifestblob_len = manifest_len;
> +
> + certificates_len = attest_call.certificates_buffer.len;
> + if (!certificates_len)
> + goto success;
> +
> + void *cbuf __free(kvfree) = kvzalloc(certificates_len, GFP_KERNEL);
> + if (!cbuf)
> + goto error;
> +
> + memcpy(cbuf, certificates_blob, certificates_len);
> + report->auxblob = no_free_ptr(cbuf);
> + report->auxblob_len = certificates_len;
> +
> +success:
> + ret = 0;
> +
> +error:
> + free_pages_exact(buffer, size);
> +
> + return ret;
> +}
> +
> static int sev_report_new(struct tsm_report *report, void *data)
> {
> struct snp_msg_cert_entry *cert_table;
> @@ -797,6 +941,13 @@ static int sev_report_new(struct tsm_report *report, void *data)
> if (desc->inblob_len != SNP_REPORT_USER_DATA_SIZE)
> return -EINVAL;
>
> + if (desc->service_provider) {
> + if (strcmp(desc->service_provider, "svsm"))
> + return -EINVAL;
> +
> + return sev_svsm_report_new(report, data);
> + }
> +
> void *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
> if (!buf)
> return -ENOMEM;
> diff --git a/drivers/virt/coco/tsm.c b/drivers/virt/coco/tsm.c
> index d1c2db83a8ca..46f230bf13ac 100644
> --- a/drivers/virt/coco/tsm.c
> +++ b/drivers/virt/coco/tsm.c
> @@ -35,7 +35,7 @@ static DECLARE_RWSEM(tsm_rwsem);
> * The attestation report format is TSM provider specific, when / if a standard
> * materializes that can be published instead of the vendor layout. Until then
> * the 'provider' attribute indicates the format of 'outblob', and optionally
> - * 'auxblob'.
> + * 'auxblob' and 'manifestblob'.
> */
>
> struct tsm_report_state {
> @@ -48,6 +48,7 @@ struct tsm_report_state {
> enum tsm_data_select {
> TSM_REPORT,
> TSM_CERTS,
> + TSM_MANIFEST,
> };
>
> static struct tsm_report *to_tsm_report(struct config_item *cfg)
> @@ -119,6 +120,74 @@ static ssize_t tsm_report_privlevel_floor_show(struct config_item *cfg,
> }
> CONFIGFS_ATTR_RO(tsm_report_, privlevel_floor);
>
> +static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
> + const char *buf, size_t len)
> +{
> + struct tsm_report *report = to_tsm_report(cfg);
> + size_t sp_len;
> + char *sp;
> + int rc;
> +
> + guard(rwsem_write)(&tsm_rwsem);
> + rc = try_advance_write_generation(report);
> + if (rc)
> + return rc;
> +
> + sp_len = (buf[len - 1] != '\n') ? len : len - 1;
This feels like it wants a sysfs_strdup().
> +
> + sp = kstrndup(buf, sp_len, GFP_KERNEL);
> + if (!sp)
> + return -ENOMEM;
> + kfree(report->desc.service_provider);
> +
> + report->desc.service_provider = sp;
> +
> + return len;
> +}
> +CONFIGFS_ATTR_WO(tsm_report_, service_provider);
> +
> +static ssize_t tsm_report_service_guid_store(struct config_item *cfg,
> + const char *buf, size_t len)
> +{
> + struct tsm_report *report = to_tsm_report(cfg);
> + int rc;
> +
> + guard(rwsem_write)(&tsm_rwsem);
> + rc = try_advance_write_generation(report);
> + if (rc)
> + return rc;
> +
> + report->desc.service_guid = guid_null;
> +
> + rc = guid_parse(buf, &report->desc.service_guid);
> + if (rc)
> + return rc;
> +
> + return len;
> +}
> +CONFIGFS_ATTR_WO(tsm_report_, service_guid);
> +
> +static ssize_t tsm_report_service_manifest_version_store(struct config_item *cfg,
> + const char *buf, size_t len)
> +{
> + struct tsm_report *report = to_tsm_report(cfg);
> + unsigned int val;
> + int rc;
> +
> + rc = kstrtouint(buf, 0, &val);
> + if (rc)
> + return rc;
> +
> + guard(rwsem_write)(&tsm_rwsem);
> + rc = try_advance_write_generation(report);
> + if (rc)
> + return rc;
> + report->desc.service_manifest_version = val;
> +
> + return len;
> +}
> +CONFIGFS_ATTR_WO(tsm_report_, service_manifest_version);
> +
> static ssize_t tsm_report_inblob_write(struct config_item *cfg,
> const void *buf, size_t count)
> {
> @@ -163,6 +232,9 @@ static ssize_t __read_report(struct tsm_report *report, void *buf, size_t count,
> if (select == TSM_REPORT) {
> out = report->outblob;
> len = report->outblob_len;
> + } else if (select == TSM_MANIFEST) {
> + out = report->manifestblob;
> + len = report->manifestblob_len;
> } else {
> out = report->auxblob;
> len = report->auxblob_len;
> @@ -188,7 +260,7 @@ static ssize_t read_cached_report(struct tsm_report *report, void *buf,
>
> /*
> * A given TSM backend always fills in ->outblob regardless of
> - * whether the report includes an auxblob or not.
> + * whether the report includes an auxblob/manifestblob or not.
> */
> if (!report->outblob ||
> state->read_generation != state->write_generation)
> @@ -224,8 +296,10 @@ static ssize_t tsm_report_read(struct tsm_report *report, void *buf,
>
> kvfree(report->outblob);
> kvfree(report->auxblob);
> + kvfree(report->manifestblob);
> report->outblob = NULL;
> report->auxblob = NULL;
> + report->manifestblob = NULL;
> rc = ops->report_new(report, provider.data);
> if (rc < 0)
> return rc;
> @@ -252,6 +326,15 @@ static ssize_t tsm_report_auxblob_read(struct config_item *cfg, void *buf,
> }
> CONFIGFS_BIN_ATTR_RO(tsm_report_, auxblob, NULL, TSM_OUTBLOB_MAX);
>
> +static ssize_t tsm_report_manifestblob_read(struct config_item *cfg, void *buf,
> + size_t count)
> +{
> + struct tsm_report *report = to_tsm_report(cfg);
> +
> + return tsm_report_read(report, buf, count, TSM_MANIFEST);
> +}
> +CONFIGFS_BIN_ATTR_RO(tsm_report_, manifestblob, NULL, TSM_OUTBLOB_MAX);
> +
> #define TSM_DEFAULT_ATTRS() \
> &tsm_report_attr_generation, \
> &tsm_report_attr_provider
> @@ -265,6 +348,9 @@ static struct configfs_attribute *tsm_report_extra_attrs[] = {
> TSM_DEFAULT_ATTRS(),
> &tsm_report_attr_privlevel,
> &tsm_report_attr_privlevel_floor,
> + &tsm_report_attr_service_provider,
> + &tsm_report_attr_service_guid,
> + &tsm_report_attr_service_manifest_version,
Shouldn't this patch come after the configfs dynamic visibility so there
is no point in the history where vestigial attributes show up?
On 4/16/24 00:37, Dan Williams wrote:
> Tom Lendacky wrote:
>> When an SVSM is present, the guest can also request attestation reports
>> from the SVSM. These SVSM attestation reports can be used to attest the
>> SVSM and any services running within the SVSM.
>>
>> Extend the config-fs attestation support to allow for an SVSM attestation
>> report. This involves creating four (4) new config-fs attributes:
>>
>> - 'service-provider' (input)
>> This attribute is used to determine whether the attestation request
>> should be sent to the specified service provider or to the SEV
>> firmware. The SVSM service provider is represented by the value
>> 'svsm'.
>>
>> - 'service_guid' (input)
>> Used for requesting the attestation of a single service within the
>> service provider. A null GUID implies that the SVSM_ATTEST_SERVICES
>> call should be used to request the attestation report. A non-null
>> GUID implies that the SVSM_ATTEST_SINGLE_SERVICE call should be used.
>>
>> - 'service_manifest_version' (input)
>> Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
>> represents a specific service manifest version be used for the
>> attestation report.
>>
>> - 'manifestblob' (output)
>> Used to return the service manifest associated with the attestation
>> report.
>>
>> Signed-off-by: Tom Lendacky <[email protected]>
>> ---
>> Documentation/ABI/testing/configfs-tsm | 69 +++++++++++
>> arch/x86/include/asm/sev.h | 31 ++++-
>> arch/x86/kernel/sev.c | 50 ++++++++
>> drivers/virt/coco/sev-guest/sev-guest.c | 151 ++++++++++++++++++++++++
>> drivers/virt/coco/tsm.c | 93 ++++++++++++++-
>> include/linux/tsm.h | 11 ++
>> 6 files changed, 402 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/ABI/testing/configfs-tsm b/Documentation/ABI/testing/configfs-tsm
>> index dd24202b5ba5..72a7acdb5258 100644
>> --- a/Documentation/ABI/testing/configfs-tsm
>> +++ b/Documentation/ABI/testing/configfs-tsm
>> @@ -31,6 +31,21 @@ Description:
>> Standardization v2.03 Section 4.1.8.1 MSG_REPORT_REQ.
>> https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf
>>
>> +What: /sys/kernel/config/tsm/report/$name/manifestblob
>> +Date: January, 2024
>> +KernelVersion: v6.10
>> +Contact: [email protected]
>> +Description:
>> + (RO) Optional supplemental data that a TSM may emit, visibility
>> + of this attribute depends on TSM, and may be empty if no
>> + manifest data is available.
>> +
>> + When @provider is "sev_guest" and the @service_provider is
>> + "svsm" this file contains the service manifest used for the SVSM
>> + attestation report from the Secure VM Service Module for SEV-SNP
>> + Guests v1.00 Section 7.
>> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
>
> Should this be "See 'service_provider' for the format of this blob"? To
> date external "format specification" links are only referenced once in
> this file, and this one is now duplicated.
Yes, I can do that for this and the other ones you identified below.
>
>
>> +
>> What: /sys/kernel/config/tsm/report/$name/provider
>> Date: September, 2023
>> KernelVersion: v6.7
>> @@ -80,3 +95,57 @@ Contact: [email protected]
>> Description:
>> (RO) Indicates the minimum permissible value that can be written
>> to @privlevel.
>> +
>> +What: /sys/kernel/config/tsm/report/$name/service_provider
>> +Date: January, 2024
>> +KernelVersion: v6.10
>> +Contact: [email protected]
>> +Description:
>> + (WO) Attribute is visible if a TSM implementation provider
>> + supports the concept of attestation reports from a service
>> + provider for TVMs, like SEV-SNP running under an SVSM.
>> + Specifying the service provider via this attribute will create
>> + an attestation report as specified by the service provider.
>> + Currently supported service-providers are:
>> + svsm
>> +
>> + For the SVSM service provider, see the Secure VM Service Module
>> + for SEV-SNP Guests v1.00 Section 7.
>> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
>
> Given "SVSM" is a cross vendor concept should this explicitly
> callout: "For provider.service_provider == sev_guest.svsm" as
> preparation for other implementations defining their "svsm" manifest
> format?
I'm not sure. Do we need to get that specific? If SVSM is cross vendor,
will it be using / adding to the existing SVSM specification? If not,
then each vendor is likely to have its own name for the SVSM concept
that would be unique enough...
>
>> +
>> +What: /sys/kernel/config/tsm/report/$name/service_manifest_version
>> +Date: January, 2024
>> +KernelVersion: v6.10
>> +Contact: [email protected]
>> +Description:
>> + (WO) Attribute is visible if a TSM implementation provider
>> + supports the concept of attestation reports from a service
>> + provider for TVMs, like SEV-SNP running under an SVSM.
>> + Indicates the service manifest version requested for the
>> + attestation report. If this field is not set by the user,
>> + the default manifest version of the service (the service's
>> + initial/first manifest version) is returned. The initial
>> + manifest version is always available.
>
> ...and that number is zero? Is there any expectation that the kernel
Yes, that number is zero.
> sanity checks this version, or how does the user figure out they need to
> roll this request back?
Right now there aren't any non-zero versions, so there is nothing for
the user to figure out. However, the service will determine when it
creates a new version and then the user will need to understand what the
reason for that is and decide. I'm not sure I can give you a specific
answer at this stage, but we need to allow for a change in the manifest
without affecting existing users.
And since the spec has been approved already, I can't really go back and
add a requirement that manifest format always be additive.
>
>> +
>> + For the SVSM service provider, see the Secure VM Service Module
>> + for SEV-SNP Guests v1.00 Section 7.
>> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
>
>> +static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
>> + const char *buf, size_t len)
>> +{
>> + struct tsm_report *report = to_tsm_report(cfg);
>> + size_t sp_len;
>> + char *sp;
>> + int rc;
>> +
>> + guard(rwsem_write)(&tsm_rwsem);
>> + rc = try_advance_write_generation(report);
>> + if (rc)
>> + return rc;
>> +
>> + sp_len = (buf[len - 1] != '\n') ? len : len - 1;
>
> This feels like it wants a sysfs_strdup().
If there start to be more string oriented operations in the file, then
it might be worth it. For now I don't really see a reason.
>
>> +
>> + sp = kstrndup(buf, sp_len, GFP_KERNEL);
>> + if (!sp)
>> + return -ENOMEM;
>> + kfree(report->desc.service_provider);
>> +
>> + report->desc.service_provider = sp;
>> +
>> + return len;
>> +}
>> +CONFIGFS_ATTR_WO(tsm_report_, service_provider);
>> +
>> #define TSM_DEFAULT_ATTRS() \
>> &tsm_report_attr_generation, \
>> &tsm_report_attr_provider
>> @@ -265,6 +348,9 @@ static struct configfs_attribute *tsm_report_extra_attrs[] = {
>> TSM_DEFAULT_ATTRS(),
>> &tsm_report_attr_privlevel,
>> &tsm_report_attr_privlevel_floor,
>> + &tsm_report_attr_service_provider,
>> + &tsm_report_attr_service_guid,
>> + &tsm_report_attr_service_manifest_version,
>
> Shouldn't this patch come after the configfs dynamic visibility so there
> is no point in the history where vestigial attributes show up?
Sure, I can do that.
Thanks,
Tom
Tom Lendacky wrote:
> On 4/16/24 00:37, Dan Williams wrote:
> > Tom Lendacky wrote:
> >> When an SVSM is present, the guest can also request attestation reports
> >> from the SVSM. These SVSM attestation reports can be used to attest the
> >> SVSM and any services running within the SVSM.
> >>
> >> Extend the config-fs attestation support to allow for an SVSM attestation
> >> report. This involves creating four (4) new config-fs attributes:
> >>
> >> - 'service-provider' (input)
> >> This attribute is used to determine whether the attestation request
> >> should be sent to the specified service provider or to the SEV
> >> firmware. The SVSM service provider is represented by the value
> >> 'svsm'.
> >>
> >> - 'service_guid' (input)
> >> Used for requesting the attestation of a single service within the
> >> service provider. A null GUID implies that the SVSM_ATTEST_SERVICES
> >> call should be used to request the attestation report. A non-null
> >> GUID implies that the SVSM_ATTEST_SINGLE_SERVICE call should be used.
> >>
> >> - 'service_manifest_version' (input)
> >> Used with the SVSM_ATTEST_SINGLE_SERVICE call, the service version
> >> represents a specific service manifest version be used for the
> >> attestation report.
> >>
> >> - 'manifestblob' (output)
> >> Used to return the service manifest associated with the attestation
> >> report.
> >>
> >> Signed-off-by: Tom Lendacky <[email protected]>
[..]
> >> +What: /sys/kernel/config/tsm/report/$name/service_provider
> >> +Date: January, 2024
> >> +KernelVersion: v6.10
> >> +Contact: [email protected]
> >> +Description:
> >> + (WO) Attribute is visible if a TSM implementation provider
> >> + supports the concept of attestation reports from a service
> >> + provider for TVMs, like SEV-SNP running under an SVSM.
> >> + Specifying the service provider via this attribute will create
> >> + an attestation report as specified by the service provider.
> >> + Currently supported service-providers are:
> >> + svsm
> >> +
> >> + For the SVSM service provider, see the Secure VM Service Module
> >> + for SEV-SNP Guests v1.00 Section 7.
> >> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
> >
> > Given "SVSM" is a cross vendor concept should this explicitly
> > callout: "For provider.service_provider == sev_guest.svsm" as
> > preparation for other implementations defining their "svsm" manifest
> > format?
>
> I'm not sure. Do we need to get that specific? If SVSM is cross vendor,
> will it be using / adding to the existing SVSM specification? If not,
> then each vendor is likely to have its own name for the SVSM concept
> that would be unique enough...
Yeah, I guess we can kick can that down the road and see what other
vendors do. I know the coconut-svsm project is cross vendor, but I do
not know the details.
> >> +
> >> +What: /sys/kernel/config/tsm/report/$name/service_manifest_version
> >> +Date: January, 2024
> >> +KernelVersion: v6.10
> >> +Contact: [email protected]
> >> +Description:
> >> + (WO) Attribute is visible if a TSM implementation provider
> >> + supports the concept of attestation reports from a service
> >> + provider for TVMs, like SEV-SNP running under an SVSM.
> >> + Indicates the service manifest version requested for the
> >> + attestation report. If this field is not set by the user,
> >> + the default manifest version of the service (the service's
> >> + initial/first manifest version) is returned. The initial
> >> + manifest version is always available.
> >
> > ...and that number is zero? Is there any expectation that the kernel
>
> Yes, that number is zero.
>
> > sanity checks this version, or how does the user figure out they need to
> > roll this request back?
>
> Right now there aren't any non-zero versions, so there is nothing for
> the user to figure out. However, the service will determine when it
> creates a new version and then the user will need to understand what the
> reason for that is and decide. I'm not sure I can give you a specific
> answer at this stage, but we need to allow for a change in the manifest
> without affecting existing users.
Right, but it feels odd that userspace could write UINT_MAX to this
value and the kernel says, "yup, looks like a valid manifest version to
me".
> And since the spec has been approved already, I can't really go back and
> add a requirement that manifest format always be additive.
Those breaking changes have not arrived yet so still a chance to
influence, no?
The documentation here at least guarantees that the initial manifest
version is always valid, and I expect the spec authors to realize that
the kernel has a role to play in not breaking existing userspace. I.e.
it is not in the spec's interest to disallow fallback to any
version between 0 and N-1 where N is the latest.
The kernel need not tolerate version induced breakage from ACPI
specification updates because that spec is committed to compatibility,
why does this spec need to be less disciplined than that?
> >> +
> >> + For the SVSM service provider, see the Secure VM Service Module
> >> + for SEV-SNP Guests v1.00 Section 7.
> >> + https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
> >
>
> >> +static ssize_t tsm_report_service_provider_store(struct config_item *cfg,
> >> + const char *buf, size_t len)
> >> +{
> >> + struct tsm_report *report = to_tsm_report(cfg);
> >> + size_t sp_len;
> >> + char *sp;
> >> + int rc;
> >> +
> >> + guard(rwsem_write)(&tsm_rwsem);
> >> + rc = try_advance_write_generation(report);
> >> + if (rc)
> >> + return rc;
> >> +
> >> + sp_len = (buf[len - 1] != '\n') ? len : len - 1;
> >
> > This feels like it wants a sysfs_strdup().
>
> If there start to be more string oriented operations in the file, then
> it might be worth it. For now I don't really see a reason.
To be clear I was thinking of occurrences of this patten outside of this
file. Turns out this pattern is not as prevalent as I would have
guessed, resource_alignment_store() was the only occurrence I could
find. Skip for now works for me.