Re: SVSM Attestation and vTPM specification additions - v0.60

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Thu, 2023-01-12 at 09:13 -0600, Tom Lendacky wrote:
> On 1/12/23 07:57, James Bottomley wrote:
> > On Wed, 2023-01-11 at 17:39 +0100, Christophe de Dinechin wrote:
> > [...]
> > > p29: Table 14: How can RAX be used as command ordinal and command
> > > response size if it's already used for call identifier / result
> > > value?
> > 
> > I think there's a bug on the first table: in the prototype we use
> > RAX [in] (not RCX [in]) for the pointer to the request/response
> > buffer and RAX [out] as the SVSM return code.
> 
> No, it's not a bug. You'll need to use RCX as the pointer to the 
> request/response buffer because RAX, per calling convention, contains
> the protocol id and call id.

Oh, right, I should have looked at the code first before commenting we
do indeed use RCX for the shared buffer.

Do you have a timetable for updating the linux-svsm github for the new
protocol based calling convention?  We'd like to rebase the new vTPM
code off it when it's available.

James