x86/kvm: Remove .fixup usage

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

Author: Peter Zijlstra

arch/x86/include/asm/extable_fixup_types.h

@@ -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

arch/x86/kvm/emulate.c

@@ -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; \
 })