On Fri, Jul 16, 2021, Brijesh Singh wrote:

On 7/16/21 2:33 PM, Sean Christopherson wrote:

quoted

On Wed, Jul 07, 2021, Brijesh Singh wrote:

quoted

diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 3fd9a7e9d90c..989a64aa1ae5 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h

@@ -1678,6 +1678,9 @@ enum sev_cmd_id {
 	/* Guest Migration Extension */
 	KVM_SEV_SEND_CANCEL,
 
+	/* SNP specific commands */
+	KVM_SEV_SNP_INIT = 256,

Is there any meaning behind '256'?  If not, why skip a big chunk?  I wouldn't be
concerned if it weren't for KVM_SEV_NR_MAX, whose existence arguably implies that
0-KVM_SEV_NR_MAX-1 are all valid SEV commands.

In previous patches, Peter highlighted that we should keep some gap
between the SEV/ES and SNP to leave room for legacy SEV/ES expansion. I
was not sure how many we need to reserve without knowing what will come
in the future; especially recently some of the command additional  are
not linked to the firmware. I am okay to reduce the gap or remove the
gap all together.

Unless the numbers themselves have meaning, which I don't think they do, I vote
to keep the arbitrary numbers contiguous.  KVM_SEV_NR_MAX makes me nervous, and
there are already cases of related commands being discontiguous, e.g. KVM_SEND_CANCEL.

Peter or Paolo, any thoughts?