Re: [edk2-devel] [PATCH v14 45/46] UefiCpuPkg/MpInitLib: Prepare SEV-ES guest APs for OS use

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

On 08/07/20 23:53, Lendacky, Thomas wrote:
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198
> 
> Before UEFI transfers control to the OS, it must park the AP. This is
> done using the AsmRelocateApLoop function to transition into 32-bit
> non-paging mode. For an SEV-ES guest, a few additional things must be
> done:
>   - AsmRelocateApLoop must be updated to support SEV-ES. This means
>     performing a VMGEXIT AP Reset Hold instead of an MWAIT or HLT loop.
>   - Since the AP must transition to real mode, a small routine is copied
>     to the WakeupBuffer area. Since the WakeupBuffer will be used by
>     the AP during OS booting, it must be placed in reserved memory.
>     Additionally, the AP stack must be located where it can be accessed
>     in real mode.
>   - Once the AP is in real mode it will transfer control to the
>     destination specified by the OS in the SEV-ES AP Jump Table. The
>     SEV-ES AP Jump Table address is saved by the hypervisor for the OS
>     using the GHCB VMGEXIT AP Jump Table exit code.
> 
> Cc: Eric Dong <eric.dong@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Reviewed-by: Eric Dong <eric.dong@intel.com>
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
> ---
>  UefiCpuPkg/Library/MpInitLib/MpLib.h          |   8 +-
>  UefiCpuPkg/Library/MpInitLib/DxeMpLib.c       |  54 +++++++-
>  .../Library/MpInitLib/Ia32/MpFuncs.nasm       |   5 +-
>  UefiCpuPkg/Library/MpInitLib/X64/MpFuncs.nasm | 130 ++++++++++++++++--
>  4 files changed, 179 insertions(+), 18 deletions(-)

this patch is indeed the v13 variant with the incremental fix that I had
tested squashed in it.

Thanks!
Laszlo