Re: [edk2-devel] [PATCH v8 22/46] OvmfPkg/VmgExitLib: Add support for VMMCALL NAE events

["Laszlo Ersek" <lersek@redhat.com>]

On 05/19/20 23:50, Lendacky, Thomas wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
> 
> Under SEV-ES, a VMMCALL intercept generates a #VC exception. VMGEXIT must
> be used to allow the hypervisor to handle this intercept.
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  .../Library/VmgExitLib/X64/VmgExitVcHandler.c | 48 +++++++++++++++++++
>  1 file changed, 48 insertions(+)
> 
> diff --git a/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c b/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
> index 0b7f24fd962c..bf1555234d69 100644
> --- a/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
> +++ b/OvmfPkg/Library/VmgExitLib/X64/VmgExitVcHandler.c
> @@ -875,6 +875,50 @@ WbinvdExit (
>    return 0;
>  }
>  
> +/**
> +  Handle a VMMCALL event.
> +
> +  Use the VMGEXIT instruction to handle either a VMMCALL event.
> +
> +  @param[in, out] Ghcb             Pointer to the Guest-Hypervisor Communication
> +                                   Block
> +  @param[in, out] Regs             x64 processor context
> +  @param[in]      InstructionData  Instruction parsing context
> +
> +  @retval 0                        Event handled successfully
> +  @retval Others                   New exception value to propagate
> +
> +**/
> +STATIC
> +UINT64
> +VmmCallExit (
> +  IN OUT GHCB                     *Ghcb,
> +  IN OUT EFI_SYSTEM_CONTEXT_X64   *Regs,
> +  IN     SEV_ES_INSTRUCTION_DATA  *InstructionData
> +  )
> +{
> +  UINT64  Status;
> +
> +  DecodeModRm (Regs, InstructionData);
> +
> +  Ghcb->SaveArea.Rax = Regs->Rax;
> +  GhcbSetRegValid (Ghcb, GhcbRax);
> +  Ghcb->SaveArea.Cpl = (UINT8) (Regs->Cs & 0x3);
> +  GhcbSetRegValid (Ghcb, GhcbCpl);
> +
> +  Status = VmgExit (Ghcb, SVM_EXIT_VMMCALL, 0, 0);
> +  if (Status) {

(1) Please write (Status > 0) or (Status != 0).

Acked-by: Laszlo Ersek <lersek@redhat.com>

Thanks
Laszlo

> +    return Status;
> +  }
> +
> +  if (!GhcbIsRegValid (Ghcb, GhcbRax)) {
> +    return UnsupportedExit (Ghcb, Regs, InstructionData);
> +  }
> +  Regs->Rax = Ghcb->SaveArea.Rax;
> +
> +  return 0;
> +}
> +
>  /**
>    Handle an MSR event.
>  
> @@ -1395,6 +1439,10 @@ VmgExitHandleVc (
>      NaeExit = MsrExit;
>      break;
>  
> +  case SVM_EXIT_VMMCALL:
> +    NaeExit = VmmCallExit;
> +    break;
> +
>    case SVM_EXIT_WBINVD:
>      NaeExit = WbinvdExit;
>      break;
>