On 1/30/2018 11:33 PM, Laszlo Ersek wrote:
SMM emulation under KVM crashes the guest when the "jz" branch, added in
commit d4d87596c11d ("UefiCpuPkg/PiSmmCpuDxeSmm: Enable NXE if it's
supported", 2018-01-18), is taken.
Rework the propagation of CPUID.80000001H:EDX.NX [bit 20] to IA32_EFER.NXE
[bit 11] so that no code is executed conditionally.
Cc: Eric Dong <eric.d...@intel.com>
Cc: Jian J Wang <jian.j.w...@intel.com>
Cc: Jiewen Yao <jiewen....@intel.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Ruiyu Ni <ruiyu...@intel.com>
Ref: d6fff558-6c4f-9ca6-74a7-e7cd9d007276@redhat.com">http://mid.mail-archive.com/d6fff558-6c4f-9ca6-74a7-e7cd9d007276@redhat.com
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <ler...@redhat.com>
---
UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
index 9231aa5b3ded..102e0bdbabc8 100644
--- a/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
+++ b/UefiCpuPkg/PiSmmCpuDxeSmm/Ia32/SmmInit.nasm
@@ -44,26 +44,25 @@ global ASM_PFX(SmmStartup)
BITS 16
ASM_PFX(SmmStartup):
mov eax, 0x80000001 ; read capability
cpuid
mov ebx, edx ; rdmsr will change edx. keep it in
ebx.
+ and ebx, BIT20 ; extract XD capability bit
Per CPUID_EXTENDED_CPU_SIG_EDX definition in
UefiCpuPkg/Include/Register/CpuId.h, the BIT name is NX.
+ shr ebx, 9 ; shift bit to IA32_EFER NXE position
How about changing above comments to:
; shift bit to IA32_EFER.NXE[BIT11] position?
DB 0x66, 0xb8 ; mov eax, imm32
ASM_PFX(gSmmCr3): DD 0
mov cr3, eax
o32 lgdt [cs:ebp + (ASM_PFX(gcSmiInitGdtr) - ASM_PFX(SmmStartup))]
DB 0x66, 0xb8 ; mov eax, imm32
ASM_PFX(gSmmCr4): DD 0
mov cr4, eax
mov ecx, 0xc0000080 ; IA32_EFER MSR
rdmsr
- test ebx, BIT20 ; check NXE capability
- jz .1
- or ah, BIT3 ; set NXE bit
+ or eax, ebx ; set NXE bit if XD is available
; Bit name is NX.
wrmsr
-.1:
DB 0x66, 0xb8 ; mov eax, imm32
ASM_PFX(gSmmCr0): DD 0
mov di, PROTECT_MODE_DS
mov cr0, eax
DB 0x66, 0xea ; jmp far [ptr48]
ASM_PFX(gSmmJmpAddr):
Very clever solution to remove jz.
With the minor comments update,
Reviewed-by: Ruiyu Ni <ruiyu...@intel.com>
--
Thanks,
Ray
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