On 9/2/21 6:26 AM, Borislav Petkov wrote:
On Mon, Aug 30, 2021 at 10:07:39AM -0500, Brijesh Singh wrote:
The SNP firmware spec says that counter must begin with the 1.
So put that in the comment and explain what 0 is: magic or invalid or
whatnot and why is that so and that it is spec-ed this way, etc.
Just having it there without a reasoning makes one wonder whether that's
some arbitrary limitation or so.
Agreed, I will add a comment explaining it.
During the GHCB writing the seqno use to be 32-bit value and hence the GHCB
spec choose the 32-bit value but recently the SNP firmware changed it from
the 32 to 64. So, now we are left with the option of limiting the sequence
number to 32-bit. If we go beyond 32-bit then all we can do is fail the
call. If we pass the value of zero then FW will fail the call.
That sounds weird again. So make it 64-bit like the FW and fix the spec.
I just choose the smaller name but I have no issues matching with the spec.
Also those keys does not have anything to do with the VMPL level. The
secrets page provides 4 different keys and they are referred as vmpck0..3
and each of them have a sequence numbers associated with it.
In GHCB v3 we probably need to rework the structure name.
You can point to the spec section so that readers can find the struct
layout there.
I will add comment that this for spec 0.9+.
thanks
