Re: [edk2-devel] [PATCH 04/12] OvmfPkg/ResetVector: Perform a simple SEV-ES sanity check

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

On 12/15/20 21:51, Lendacky, Thomas wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3108
> 
> If a hypervisor incorrectly reports through CPUID that SEV-ES is not
> active, ensure that a #VC exception was not taken. If it is found that
> a #VC was taken, then the code enters a HLT loop.
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index 3cd909df4f09..b08f31157cbf 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -153,6 +153,21 @@ SevEncBitLowHlt:
>      jmp       SevEncBitLowHlt
>  
>  NoSev:
> +    ;
> +    ; Perform an SEV-ES sanity check by seeing if a #VC exception occurred.
> +    ;
> +    cmp       byte[SEV_ES_WORK_AREA], 0
> +    jz        NoSevPass
> +
> +    ;
> +    ; A #VC was received, yet CPUID indicates no SEV-ES support, something
> +    ; isn't right.
> +    ;
> +NoSevEsVcHlt:
> +    hlt
> +    jmp       NoSevEsVcHlt
> +
> +NoSevPass:
>      xor       eax, eax
>  
>  SevExit:
> 

(Please consider the CLI question for this patch as well.)

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

Thanks
Laszlo