[PATCH v1 26/26] crypto: ccp: Add the SNP_SET_CONFIG command

Michael Roth
2023-12-30T16:28:06Z

From: Brijesh Singh <brijesh.singh@amd.com>

The SEV-SNP firmware provides the SNP_CONFIG command used to set various
system-wide configuration values for SNP guests, such as the TCB version
to be reported in guest attestation reports. Add an interface to set
this via userspace.

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, drop extended request/certificate
handling and simplify this to a simple wrapper around SNP_CONFIG fw
cmd]
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
Documentation/virt/coco/sev-guest.rst | 13 +++++++++++++
drivers/crypto/ccp/sev-dev.c | 20 ++++++++++++++++++++
include/uapi/linux/psp-sev.h | 1 +
3 files changed, 34 insertions(+)

diff --git a/Documentation/virt/coco/sev-guest.rst b/Documentation/virt/coco/sev-guest.rst
index 007ae828aa2a..4f696aacc866 100644
--- a/Documentation/virt/coco/sev-guest.rst
+++ b/Documentation/virt/coco/sev-guest.rst
@@ -162,6 +162,19 @@ SEV-SNP firmware SNP_COMMIT command. This prevents roll-back to a previously
committed firmware version. This will also update the reported TCB to match
that of the currently installed firmware.

+2.6 SNP_SET_CONFIG
+------------------
+:Technology: sev-snp
+:Type: hypervisor ioctl cmd
+:Parameters (in): struct sev_user_data_snp_config
+:Returns (out): 0 on success, -negative on error
+
+The SNP_SET_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 current values of the
+firmware parameters affected by this command can be queried via
+SNP_PLATFORM_STATUS.
+
3. SEV-SNP CPUID Enforcement
============================

diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
index 9c051a9b43e2..c5b26b3fe7ff 100644
--- a/drivers/crypto/ccp/sev-dev.c
+++ b/drivers/crypto/ccp/sev-dev.c
@@ -2018,6 +2018,23 @@ static int sev_ioctl_do_snp_commit(struct sev_issue_cmd *argp)
return __sev_do_cmd_locked(SEV_CMD_SNP_COMMIT, &buf, &argp->error);
}

+static int sev_ioctl_do_snp_set_config(struct sev_issue_cmd *argp, bool writable)
+{
+ struct sev_device *sev = psp_master->sev_data;
+ struct sev_user_data_snp_config config;
+
+ if (!sev->snp_initialized || !argp->data)
+ return -EINVAL;
+
+ if (!writable)
+ return -EPERM;
+
+ if (copy_from_user(&config, (void __user *)argp->data, sizeof(config)))
+ return -EFAULT;
+
+ return __sev_do_cmd_locked(SEV_CMD_SNP_CONFIG, &config, &argp->error);
+}
+
static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
{
void __user *argp = (void __user *)arg;
@@ -2075,6 +2092,9 @@ static long sev_ioctl(struct file *file, unsigned int ioctl, unsigned long arg)
case SNP_COMMIT:
ret = sev_ioctl_do_snp_commit(&input);
break;
+ case SNP_SET_CONFIG:
+ ret = sev_ioctl_do_snp_set_config(&input, writable);
+ break;
default:
ret = -EINVAL;
goto out;
diff --git a/include/uapi/linux/psp-sev.h b/include/uapi/linux/psp-sev.h
index 01aab4b340f4..f28d4fb5bc21 100644
--- a/include/uapi/linux/psp-sev.h
+++ b/include/uapi/linux/psp-sev.h
@@ -30,6 +30,7 @@ enum {
SEV_GET_ID2,
SNP_PLATFORM_STATUS,
SNP_COMMIT,
+ SNP_SET_CONFIG,

SEV_MAX,
};
--
2.25.1