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x86/kvm: Remove .fixup usage

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KVM instruction emulation has a gnarly hack where the .fixup does a
return, however there's already a ret right after the 10b label, so
mark that as 11 and have the exception clear %esi to remove the
.fixup.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20211110101325.722157053@infradead.org
This commit is contained in:
Peter Zijlstra 2021-11-10 11:01:16 +01:00
parent 5fc77b916c
commit c9a34c3f4e
2 changed files with 5 additions and 12 deletions
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1
arch/x86/include/asm/extable_fixup_types.h
View File

@ -46,5 +46,6 @@
#define EX_TYPE_IMM_REG 17 /* reg := (long)imm */
#define EX_TYPE_EFAULT_REG (EX_TYPE_IMM_REG | EX_DATA_IMM(-EFAULT))
#define EX_TYPE_ZERO_REG (EX_TYPE_IMM_REG | EX_DATA_IMM(0))
#define EX_TYPE_ONE_REG (EX_TYPE_IMM_REG | EX_DATA_IMM(1))
#endif

16
arch/x86/kvm/emulate.c
View File

@ -315,7 +315,7 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
__FOP_FUNC(#name)
#define __FOP_RET(name) \
ASM_RET \
"11: " ASM_RET \
".size " name ", .-" name "\n\t"
#define FOP_RET(name) \
@ -344,7 +344,7 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
__FOP_RET(#op "_" #dst)
#define FOP1EEX(op, dst) \
FOP1E(op, dst) _ASM_EXTABLE(10b, kvm_fastop_exception)
FOP1E(op, dst) _ASM_EXTABLE_TYPE_REG(10b, 11b, EX_TYPE_ZERO_REG, %%esi)
#define FASTOP1(op) \
FOP_START(op) \
@ -434,10 +434,6 @@ static int fastop(struct x86_emulate_ctxt *ctxt, fastop_t fop);
#op " %al \n\t" \
__FOP_RET(#op)
asm(".pushsection .fixup, \"ax\"\n"
"kvm_fastop_exception: xor %esi, %esi; " ASM_RET
".popsection");
FOP_START(setcc)
FOP_SETCC(seto)
FOP_SETCC(setno)
@ -473,12 +469,8 @@ FOP_END;
\
asm volatile("1:" insn "\n" \
"2:\n" \
".pushsection .fixup, \"ax\"\n" \
"3: movl $1, %[_fault]\n" \
" jmp 2b\n" \
".popsection\n" \
_ASM_EXTABLE(1b, 3b) \
: [_fault] "+qm"(_fault) inoutclob ); \
_ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_ONE_REG, %[_fault]) \
: [_fault] "+r"(_fault) inoutclob ); \
\
_fault ? X86EMUL_UNHANDLEABLE : X86EMUL_CONTINUE; \
})