Re: [PATCH v9 36/46] OvmfPkg/ResetVector: Add support for a 32-bit SEV check

["Laszlo Ersek" <lersek@redhat.com>]

On 06/05/20 15:27, Tom Lendacky wrote:
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
> 
> During BSP startup, the reset vector code will issue a CPUID instruction
> while in 32-bit mode. When running as an SEV-ES guest, this will trigger
> a #VC exception.
> 
> Add exception handling support to the early reset vector code to catch
> these exceptions.  Also, since the guest is in 32-bit mode at this point,
> writes to the GHCB will be encrypted and thus not able to be read by the
> hypervisor, so use the GHCB CPUID request/response protocol to obtain the
> requested CPUID function values and provide these to the guest.
> 
> The exception handling support is active during the SEV check and uses the
> OVMF temporary RAM space for a stack. After the SEV check is complete, the
> exception handling support is removed and the stack pointer cleared.
> 
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
> Reviewed-by: Laszlo Ersek <lersek@redhat.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
> 
> This patch has been reverted to the previous v6 version.
> ---
>  OvmfPkg/ResetVector/ResetVector.inf       |   3 +
>  OvmfPkg/ResetVector/Ia32/PageTables64.asm | 275 +++++++++++++++++++-
>  OvmfPkg/ResetVector/ResetVector.nasmb     |   2 +
>  3 files changed, 277 insertions(+), 3 deletions(-)

Thanks!
Laszlo