[PATCH RFC v7 63/64] x86/sev: Document KVM_SEV_SNP_{G,S}ET_CERTS

[Michael Roth <michael.roth@amd.com>]

From: Dionna Glaze <dionnaglaze@google.com>

Update the KVM_MEMORY_ENCRYPT_OP documentation to include the new
commands for overriding the host certificates that the guest receives
from an extended guest request.

Cc: Thomas Lendacky <Thomas.Lendacky@amd.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
---
 .../virt/kvm/x86/amd-memory-encryption.rst    | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
index e4b42aaab1de..3cfe7b7cef61 100644
--- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
@@ -536,6 +536,50 @@ Returns: 0 on success, -negative on error
 
 See SEV-SNP specification for further details on launch finish input parameters.
 
+22. KVM_SEV_SNP_GET_CERTS
+-------------------------
+
+After the SNP guest launch flow has started, the KVM_SEV_SNP_GET_CERTS command
+can be issued to request the data that has been installed with the
+KVM_SEV_SNP_SET_CERTS command.
+
+Parameters (in/out): struct kvm_sev_snp_get_certs
+
+Returns: 0 on success, -negative on error
+
+::
+
+	struct kvm_sev_snp_get_certs {
+		__u64 certs_uaddr;
+		__u64 certs_len
+	};
+
+If no certs have been installed, then the return value is -ENOENT.
+If the buffer specified in the struct is too small, the certs_len field will be
+overwritten with the required bytes to receive all the certificate bytes and the
+return value will be -EINVAL.
+
+23. KVM_SEV_SNP_SET_CERTS
+-------------------------
+
+After the SNP guest launch flow has started, the KVM_SEV_SNP_SET_CERTS command
+can be issued to override the /dev/sev certs data that is returned when a
+guest issues an extended guest request. This is useful for instance-specific
+extensions to the host certificates.
+
+Parameters (in/out): struct kvm_sev_snp_set_certs
+
+Returns: 0 on success, -negative on error
+
+::
+
+	struct kvm_sev_snp_set_certs {
+		__u64 certs_uaddr;
+		__u64 certs_len
+	};
+
+The certs_len field may not exceed SEV_FW_BLOB_MAX_SIZE.
+
 References
 ==========
 
-- 
2.25.1