[edk2-devel] [PATCH v2 04/15] OvmfPkg/ResetVector: Perform a simple SEV-ES sanity check

[Laszlo Ersek]

On 01/06/21 22:21, Lendacky, Thomas wrote:
> From: Tom Lendacky <thomas.lendacky at 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 at intel.com>
> Cc: Laszlo Ersek <lersek at redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel at arm.com>
> Cc: Brijesh Singh <brijesh.singh at amd.com>
> Reviewed-by: Laszlo Ersek <lersek at redhat.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky at amd.com>
> ---
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)

Thanks for the update!
Laszlo

> 
> diff --git a/OvmfPkg/ResetVector/Ia32/PageTables64.asm b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> index ccc95ad4715d..a1771dfdec23 100644
> --- a/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> +++ b/OvmfPkg/ResetVector/Ia32/PageTables64.asm
> @@ -154,6 +154,22 @@ 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:
> +    cli
> +    hlt
> +    jmp       NoSevEsVcHlt
> +
> +NoSevPass:
>      xor       eax, eax
>  
>  SevExit:
> 



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