audk/UefiCpuPkg/ResetVector/Vtf0/Ia16
Tom Lendacky 0d7601e546 UefiCpuPkg: Add a 16-bit protected mode code segment descriptor
BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=2198

A hypervisor is not allowed to update an SEV-ES guests register state,
so when booting an SEV-ES guest AP, the hypervisor is not allowed to
set the RIP to the guest requested value. Instead, an SEV-ES AP must be
transition from 64-bit long mode to 16-bit real mode in response to an
INIT-SIPI-SIPI sequence. This requires a 16-bit code segment descriptor.
For PEI, create this descriptor in the reset vector GDT table. For DXE,
create this descriptor from the newly reserved entry at location 0x28.

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>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
2020-08-17 02:46:39 +00:00
..
Init16.asm UefiCpuPkg: Replace BSD License with BSD+Patent License 2019-04-09 10:58:28 -07:00
Real16ToFlat32.asm UefiCpuPkg: Add a 16-bit protected mode code segment descriptor 2020-08-17 02:46:39 +00:00
ResetVectorVtf0.asm UefiCpuPkg: Replace BSD License with BSD+Patent License 2019-04-09 10:58:28 -07:00