[PATCH RFC v9 48/51] crypto: ccp: Add the SNP_{SET,GET}_EXT_CONFIG command

Michael Roth
2023-06-12T04:56:21Z

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