On 09/20/19 15:16, Lendacky, Thomas wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
>
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
>
> After having transitioned from UEFI to the OS, the OS will need to boot
> the APs. For an SEV-ES guest, the APs will have been parked by UEFI using
> GHCB pages allocated by UEFI. The hypervisor will write to the GHCB
> SW_EXITINFO2 field of the GHCB when the AP is booted. As a result, the
> GHCB pages must be marked reserved so that the OS does not attempt to use
> them and experience memory corruption because of the hypervisor write.
>
> Change the GHCB allocation from the default boot services memory to
> reserved memory.
>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> OvmfPkg/PlatformPei/AmdSev.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
> index d6733447bdf2..53eeb59702ae 100644
> --- a/OvmfPkg/PlatformPei/AmdSev.c
> +++ b/OvmfPkg/PlatformPei/AmdSev.c
> @@ -49,9 +49,11 @@ AmdSevEsInitialize (
>
> //
> // Allocate GHCB pages.
> + // Since the pages must survive across the UEFI to OS transition
> + // make them reserved.
> //
> GhcbPageCount = mMaxCpuCount * 2;
> - GhcbBase = AllocatePages (GhcbPageCount);
> + GhcbBase = AllocateReservedPages (GhcbPageCount);
> ASSERT (GhcbBase);
>
> GhcbBasePa = (PHYSICAL_ADDRESS)(UINTN) GhcbBase;
>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
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