Re: [PATCH 3/4] OvmfPkg/CcExitLib: Fix SEV-SNP XSave area size calculation

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 12/21/22 10:06, Michael Roth wrote:
> CPUID leaf 0xD sub-leafs 0x0 and 0x1 contain cumulative sizes for the
> enabled XSave areas. Those sizes are calculated by tallying up all the
> other sub-leafs that contain per-area size information for XSave areas
> that are currently enabled in XCr0/XSS. The current check has the logic
> inverted. Fix that.
> 
> This doesn't seem to cause problems currently, but could in the future
> if OVMF made more extensive use of XSave areas. It was noticed while
> implementing SNP-related tests for KVM Unit Tests, which re-uses the
> OVMF #VC handler in some cases.
> 
> Reported-by: Pavan Kumar Paluri <papaluri@amd.com>
> Cc: Pavan Kumar Paluri <papaluri@amd.com>
> Signed-off-by: Michael Roth <michael.roth@amd.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
>   OvmfPkg/Library/CcExitLib/CcExitVcHandler.c | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> index 985e547977..cd117d5a31 100644
> --- a/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> +++ b/OvmfPkg/Library/CcExitLib/CcExitVcHandler.c
> @@ -1678,9 +1678,7 @@ GetCpuidXSaveSize (
>     for (Idx = 0; Idx < CpuidInfo->Count; Idx++) {
>       SEV_SNP_CPUID_FUNCTION  *CpuidFn = &CpuidInfo->function[Idx];
>   
> -    if (!((CpuidFn->EaxIn == 0xD) &&
> -          ((CpuidFn->EcxIn == 0) || (CpuidFn->EcxIn == 1))))
> -    {
> +    if (!((CpuidFn->EaxIn == 0xD) && (CpuidFn->EcxIn > 1))) {
>         continue;
>       }
>