Re: [PATCH v11 4/4] OvmfPkg/PlatformPei: SEV-SNP make >=4GB unaccepted

["Ard Biesheuvel" <ardb@kernel.org>]

On Thu, 26 Jan 2023 at 22:17, Dionna Glaze <dionnaglaze@google.com> wrote:
>
> Instead of eagerly accepting all memory in PEI, only accept memory under
> the 4GB address. This allows a loaded image to use the
> MEMORY_ACCEPTANCE_PROTOCOL to disable the accept behavior and indicate
> that it can interpret the memory type accordingly.
>
> This classification is safe since ExitBootServices will accept and
> reclassify the memory as conventional if the disable protocol is not
> used.
>
> Cc: Ard Biescheuvel <ardb@kernel.org>
> Cc: "Min M. Xu" <min.m.xu@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Tom Lendacky <Thomas.Lendacky@amd.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
>
> Signed-off-by: Dionna Glaze <dionnaglaze@google.com>
> ---
>  OvmfPkg/PlatformPei/AmdSev.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/OvmfPkg/PlatformPei/AmdSev.c b/OvmfPkg/PlatformPei/AmdSev.c
> index e4e7b72e67..7d824cc282 100644
> --- a/OvmfPkg/PlatformPei/AmdSev.c
> +++ b/OvmfPkg/PlatformPei/AmdSev.c
> @@ -16,6 +16,7 @@
>  #include <Library/MemEncryptSevLib.h>
>  #include <Library/MemoryAllocationLib.h>
>  #include <Library/PcdLib.h>
> +#include <Pi/PrePiHob.h>
>  #include <PiPei.h>
>  #include <Register/Amd/Msr.h>
>  #include <Register/Intel/SmramSaveStateMap.h>
> @@ -63,6 +64,10 @@ AmdSevSnpInitialize (
>    for (Hob.Raw = GetHobList (); !END_OF_HOB_LIST (Hob); Hob.Raw = GET_NEXT_HOB (Hob)) {
>      if ((Hob.Raw != NULL) && (GET_HOB_TYPE (Hob) == EFI_HOB_TYPE_RESOURCE_DESCRIPTOR)) {
>        ResourceHob = Hob.ResourceDescriptor;
> +      if (ResourceHob->PhysicalStart >= SIZE_4GB) {

Shouldn't this check be inside the if () below? Or are all resources
that start at or above 4 GiB guaranteed to be system memory?

No need to resend - if needed, I can fix that up when applying.


> +        ResourceHob->ResourceType = BZ3937_EFI_RESOURCE_MEMORY_UNACCEPTED;
> +        continue;
> +      }
>
>        if (ResourceHob->ResourceType == EFI_RESOURCE_SYSTEM_MEMORY) {
>          MemEncryptSevSnpPreValidateSystemRam (
> --
> 2.39.1.456.gfc5497dd1b-goog
>