[PATCH] KVM: x86: document behavior of measurement ioctls with len==0

From: Paolo Bonzini
Date: Tue Apr 20 2021 - 05:34:20 EST


Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
Documentation/virt/kvm/amd-memory-encryption.rst | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/Documentation/virt/kvm/amd-memory-encryption.rst b/Documentation/virt/kvm/amd-memory-encryption.rst
index 469a6308765b..34ce2d1fcb89 100644
--- a/Documentation/virt/kvm/amd-memory-encryption.rst
+++ b/Documentation/virt/kvm/amd-memory-encryption.rst
@@ -148,6 +148,9 @@ measurement. Since the guest owner knows the initial contents of the guest at
boot, the measurement can be verified by comparing it to what the guest owner
expects.

+If len is zero on entry, the measurement blob length is written to len and
+uaddr is unused.
+
Parameters (in): struct kvm_sev_launch_measure

Returns: 0 on success, -negative on error
@@ -271,6 +274,9 @@ report containing the SHA-256 digest of the guest memory and VMSA passed through
commands and signed with the PEK. The digest returned by the command should match the digest
used by the guest owner with the KVM_SEV_LAUNCH_MEASURE.

+If len is zero on entry, the measurement blob length is written to len and
+uaddr is unused.
+
Parameters (in): struct kvm_sev_attestation

Returns: 0 on success, -negative on error
--
2.26.2