Re: [PATCH v2 3/3] OvmfPkg/PlatformPei: Mark SEC GHCB page in the page encryption bitmap.

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

On 12/3/20 4:27 PM, Ashish Kalra wrote:
> From: Ashish Kalra <ashish.kalra@amd.com>
> 
> Mark the SEC GHCB page that is mapped as unencrypted in
> ResetVector code in the hypervisor page encryption bitmap.
> 
> 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/PlatformPei/AmdSev.c | 10 ++++++++++
>   1 file changed, 10 insertions(+)
> 
> diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
> index 4a515a4847..456d32be84 100644
> --- a/OvmfPkg/PlatformPei/AmdSev.c
> +++ b/OvmfPkg/PlatformPei/AmdSev.c
> @@ -15,6 +15,7 @@
>   #include <Library/HobLib.h>
>   #include <Library/MemEncryptSevLib.h>
>   #include <Library/MemoryAllocationLib.h>
> +#include <Library/MemEncryptHypercallLib.h>
>   #include <Library/PcdLib.h>
>   #include <PiPei.h>
>   #include <Register/Amd/Cpuid.h>
> @@ -77,6 +78,15 @@ AmdSevEsInitialize (
>   
>     ZeroMem (GhcbBase, EFI_PAGES_TO_SIZE (GhcbPageCount));
>   
> +  //
> +  // GHCB_BASE setup during reset-vector needs to be marked as
> +  // decrypted in the hypervisor page encryption bitmap.
> +  //
> +  SetMemoryEncDecHypercall3 (FixedPcdGet32 (PcdOvmfSecGhcbBase),
> +    EFI_SIZE_TO_PAGES(FixedPcdGet32 (PcdOvmfSecGhcbSize)),
> +    FALSE
> +    );
> +

This seems like an odd place to add this. Why not near the top of the 
function just after setting the PcdSevEsIsEnabled PCD, rather than in the 
middle of setting up the new GHCB pages.

Thanks,
Tom

>     PcdStatus = PcdSet64S (PcdGhcbBase, GhcbBasePa);
>     ASSERT_RETURN_ERROR (PcdStatus);
>     PcdStatus = PcdSet64S (PcdGhcbSize, EFI_PAGES_TO_SIZE (GhcbPageCount));
>