Re: [PATCH v5 2/4] OvmfPkg/VmgExitLib: Add support for hypercalls with SEV-ES.

["Ashish Kalra" <ashish.kalra@amd.com>]

Hello Tom,

On Fri, Jul 16, 2021 at 09:16:00AM -0500, Tom Lendacky wrote:
> On 7/8/21 9:08 AM, Ashish Kalra wrote:
> > From: Ashish Kalra <ashish.kalra@amd.com>
> > 
> 
> The subject isn't correct since the #VC handler already supports
> hypercalls. It should say something like "Make the #VC handler aware of
> the encryption state change hypercall" or "Update the #VC handler to
> support the encryption state change hypercall" or something like that.
> 

Ok.

> > Make the VC handler hypercall aware by adding support
> > to compare the hypercall number and add the additional
> > register values used by hypercall in the GHCB.
> > 
> > Also mark the SEC GHCB page (that is mapped as
> > unencrypted in ResetVector code) in the hypervisor
> > guest page status tracking.
> 
> This part of the commit message shoudn't be here any more.
> 

Yes.

> > 
> > Cc: Jordan Justen <jordan.l.justen@intel.com>
> > Cc: Laszlo Ersek <lersek@redhat.com>
> > Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
> > ---
> >  OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
> > index 41b0c8cc53..7f69bfab5f 100644
> > --- a/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
> > +++ b/OvmfPkg/Library/VmgExitLib/VmgExitVcHandler.c
> > @@ -1171,6 +1171,15 @@ VmmCallExit (
> >    Ghcb->SaveArea.Cpl = (UINT8) (Regs->Cs & 0x3);
> >    VmgSetOffsetValid (Ghcb, GhcbCpl);
> >  
> 
> Add a comment that this hypercall requires these extra registers so you
> are explicitly adding them.
> 
Ok.

Thanks,
Ashish 

> > +  if (Regs->Rax == KVM_HC_MAP_GPA_RANGE) {
> > +    Ghcb->SaveArea.Rbx = Regs->Rbx;
> > +    VmgSetOffsetValid (Ghcb, GhcbRbx);
> > +    Ghcb->SaveArea.Rcx = Regs->Rcx;
> > +    VmgSetOffsetValid (Ghcb, GhcbRcx);
> > +    Ghcb->SaveArea.Rdx = Regs->Rdx;
> > +    VmgSetOffsetValid (Ghcb, GhcbRdx);
> > +  }
> > +
> >    Status = VmgExit (Ghcb, SVM_EXIT_VMMCALL, 0, 0);
> >    if (Status != 0) {
> >      return Status;
> >