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| author | Tom Lendacky <thomas.lendacky@amd.com> | 2020-08-12 15:21:42 -0500 |
|---|---|---|
| committer | mergify[bot] <37929162+mergify[bot]@users.noreply.github.com> | 2020-08-17 02:46:39 +0000 |
| commit | 0d7601e5467a710cbdda4edf88440dbb6a334b6e (patch) | |
| tree | 5c28ee99ba9e2c1f750c14392bffaeca2f0f0d86 /UefiCpuPkg/ResetVector/Vtf0 | |
| parent | 437eb3f7a8db7681afe0e6064d3a8edb12abb766 (diff) | |
| download | edk2-0d7601e5467a710cbdda4edf88440dbb6a334b6e.tar.gz edk2-0d7601e5467a710cbdda4edf88440dbb6a334b6e.tar.bz2 edk2-0d7601e5467a710cbdda4edf88440dbb6a334b6e.zip | |
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>
Diffstat (limited to 'UefiCpuPkg/ResetVector/Vtf0')
| -rw-r--r-- | UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm index ce4ebfffb6..0e79a3984b 100644 --- a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm +++ b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm @@ -129,5 +129,14 @@ LINEAR_CODE64_SEL equ $-GDT_BASE DB 0 ; base 31:24
%endif
+; linear code segment descriptor
+LINEAR_CODE16_SEL equ $-GDT_BASE
+ DW 0xffff ; limit 15:0
+ DW 0 ; base 15:0
+ DB 0 ; base 23:16
+ DB PRESENT_FLAG(1)|DPL(0)|SYSTEM_FLAG(1)|DESC_TYPE(CODE32_TYPE)
+ DB GRANULARITY_FLAG(1)|DEFAULT_SIZE32(0)|CODE64_FLAG(0)|UPPER_LIMIT(0xf)
+ DB 0 ; base 31:24
+
GDT_END:
|