Without the a32 modifier under FLAT32_JUMP, and the a16 modifier under LONG_JUMP, nasm doesn't generate the 0x67 prefixes, and the far jumps don't work. (For the former, KVM returns an emulation failure. For the latter, KVM performs a triple fault (guest reboot).) By forcing the 0x67 prefixes we end up with the same machine code as the one open-coded in "MpFuncs.asm".
This bug breaks S3 resume in the Ia32X64 + SMM_REQUIRE build of OVMF. Cc: Liming Gao <liming....@intel.com> Cc: Jordan Justen <jordan.l.jus...@intel.com> Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Laszlo Ersek <ler...@redhat.com> --- UefiCpuPkg/PiSmmCpuDxeSmm/X64/MpFuncs.nasm | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/MpFuncs.nasm b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/MpFuncs.nasm index 3efc4c3642b9..702233d6e49d 100644 --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/MpFuncs.nasm +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/MpFuncs.nasm @@ -83,7 +83,7 @@ o32 lidt [cs:si] FLAT32_JUMP: - jmp dword 0x20:0x0 +a32 jmp dword 0x20:0x0 BITS 32 PMODE_ENTRY: ; protected mode entry point @@ -114,7 +114,7 @@ o16 mov ss, ax ; Flat mode setup. LONG_JUMP: - jmp dword 0x38:0x0 +a16 jmp dword 0x38:0x0 BITS 64 LongModeStart: -- 1.8.3.1 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
