diff options
| author | Arthur Heymans <arthur@aheymans.xyz> | 2022-10-26 11:49:32 +0200 |
|---|---|---|
| committer | Felix Held <felix-coreboot@felixheld.de> | 2023-08-21 12:14:25 +0000 |
| commit | db766c702ac297ffe12c182d982fd0c1743a0c4c (patch) | |
| tree | e218d2e6aab39f6f598cb5fe42101c01173ce550 /src/cpu/x86 | |
| parent | 563f7afa0481bfe0d194467b80404eb32e8a4d44 (diff) | |
cpu/x86/smm: Don't save EFER
The EFER MSR is in the SMM save state and RSM properly restores it.
Returning to 32bit mode was only done so that fxsave was done in the
same mode as fxrstor, but this is no longer done.
See commit 1efca4d570 (cpu/x86/smm: Drop fxsave/fxrstor logic)
TESTED on qemu: the smihandler works fine.
Change-Id: Ie0e9584afd1f08f51ca57da5c4350042699f130d
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/68895
Reviewed-by: Paul Menzel <paulepanter@mailbox.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Diffstat (limited to 'src/cpu/x86')
| -rw-r--r-- | src/cpu/x86/smm/smm_stub.S | 43 |
1 files changed, 5 insertions, 38 deletions
diff --git a/src/cpu/x86/smm/smm_stub.S b/src/cpu/x86/smm/smm_stub.S index 673ab2c50c..f97ab59cd9 100644 --- a/src/cpu/x86/smm/smm_stub.S +++ b/src/cpu/x86/smm/smm_stub.S @@ -183,37 +183,22 @@ apicid_end: movl $0, 4(%ebx) #endif - /* Create stack frame by pushing a NULL stack base pointer */ - pushl $0x0 - mov %esp, %ebp - - /* Allocate locals (efer_backup) */ - subl $0x8, %esp - align_stack: /* Align stack to 16 bytes. Another 32 bytes are pushed below. */ andl $0xfffffff0, %esp + /* Call into the c-based SMM relocation function with the platform + * parameters. Equivalent to: + * struct arg = { cpu_num, canary }; + * c_handler(&arg) + */ #if ENV_X86_64 mov %ecx, %edi - /* Backup IA32_EFER. Preserves ebx. */ - movl $(IA32_EFER), %ecx - rdmsr - movl %eax, -0x4(%ebp) - movl %edx, -0x8(%ebp) - /* entry64.inc preserves ebx, esi, edi, ebp */ #include <cpu/x86/64bit/entry64.inc> mov %edi, %ecx -#endif - /* Call into the c-based SMM relocation function with the platform - * parameters. Equivalent to: - * struct arg = { cpu_num, canary }; - * c_handler(&arg) - */ -#if ENV_X86_64 push %rbx /* uintptr_t *canary */ push %rcx /* size_t cpu */ @@ -221,24 +206,6 @@ align_stack: movabs c_handler, %eax call *%rax - - /* - * The only reason to go back to protected mode is that RSM doesn't restore - * MSR registers and MSR IA32_EFER was modified by entering long mode. - * Drop to protected mode to safely operate on the IA32_EFER MSR. - */ - - /* Disable long mode. */ - #include <cpu/x86/64bit/exit32.inc> - - /* Restore IA32_EFER as RSM doesn't restore MSRs. */ - movl $(IA32_EFER), %ecx - rdmsr - movl -0x4(%ebp), %eax - movl -0x8(%ebp), %edx - - wrmsr - #else push $0x0 /* Padding */ push %ebx /* uintptr_t *canary */ |