Since DIV and IDIV can generate exceptions, we need an additional output
parameter indicating whether an execption has occured. To avoid increasing
register pressure on i386, we use %rsi, which is already allocated for
the fastop code pointer.
Signed-off-by: Avi Kivity <avi.kiv...@gmail.com>
---
arch/x86/kvm/emulate.c | 51 +++++++++++++++++++++++++-------------------------
1 file changed, 26 insertions(+), 25 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 0f0c15e..89f56bb 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -180,6 +180,7 @@
* src: rdx (in/out)
* src2: rcx (in)
* flags: rflags (in/out)
+ * ex: rsi (in:nonzero, out:zero if exception)
*
* Moreover, they are all exactly FASTOP_SIZE bytes long, so functions for
* different operand sizes can be reached by calculation, rather than a jump
@@ -467,7 +468,10 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void
(*fop)(struct fastop *));
#define FOPNOP() FOP_ALIGN FOP_RET
#define FOP1E(op, dst) \
- FOP_ALIGN #op " %" #dst " \n\t" FOP_RET
+ FOP_ALIGN "10: " #op " %" #dst " \n\t" FOP_RET
+
+#define FOP1EEX(op, dst) \
+ FOP1E(op, dst) _ASM_EXTABLE(10b, kvm_fastop_exception)
#define FASTOP1(op) \
FOP_START(op) \
@@ -486,6 +490,15 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void
(*fop)(struct fastop *));
ON64(FOP1E(op, rcx)) \
FOP_END
+/* 1-operand, using src2 (for MUL/DIV r/m), with exceptions */
+#define FASTOP1SRC2EX(op, name) \
+ FOP_START(name) \
+ FOP1EEX(op, cl) \
+ FOP1EEX(op, cx) \
+ FOP1EEX(op, ecx) \
+ ON64(FOP1EEX(op, rcx)) \
+ FOP_END
+
#define FOP2E(op, dst, src) \
FOP_ALIGN #op " %" #src ", %" #dst " \n\t" FOP_RET
@@ -530,6 +543,9 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void
(*fop)(struct fastop *));
/* Special case for SETcc - 1 instruction per cc */
#define FOP_SETCC(op) ".align 4; " #op " %al; ret \n\t"
+asm(".global kvm_fastop_exception \n"
+ "kvm_fastop_exception: xor %esi, %esi; ret");
+
FOP_START(setcc)
FOP_SETCC(seto)
FOP_SETCC(setno)
@@ -1001,6 +1017,8 @@ FASTOP2(test);
FASTOP1SRC2(mul, mul_ex);
FASTOP1SRC2(imul, imul_ex);
+FASTOP1SRC2EX(div, div_ex);
+FASTOP1SRC2EX(idiv, idiv_ex);
FASTOP3WCL(shld);
FASTOP3WCL(shrd);
@@ -2116,26 +2134,6 @@ static int em_jmp_far(struct x86_emulate_ctxt *ctxt)
return X86EMUL_CONTINUE;
}
-static int em_div_ex(struct x86_emulate_ctxt *ctxt)
-{
- u8 de = 0;
-
- emulate_1op_rax_rdx(ctxt, "div", de);
- if (de)
- return emulate_de(ctxt);
- return X86EMUL_CONTINUE;
-}
-
-static int em_idiv_ex(struct x86_emulate_ctxt *ctxt)
-{
- u8 de = 0;
-
- emulate_1op_rax_rdx(ctxt, "idiv", de);
- if (de)
- return emulate_de(ctxt);
- return X86EMUL_CONTINUE;
-}
-
static int em_grp45(struct x86_emulate_ctxt *ctxt)
{
int rc = X86EMUL_CONTINUE;
@@ -3700,8 +3698,8 @@ static const struct opcode group3[] = {
F(DstMem | SrcNone | Lock, em_neg),
F(DstXacc | Src2Mem, em_mul_ex),
F(DstXacc | Src2Mem, em_imul_ex),
- I(DstXacc | Src2Mem, em_div_ex),
- I(DstXacc | Src2Mem, em_idiv_ex),
+ F(DstXacc | Src2Mem, em_div_ex),
+ F(DstXacc | Src2Mem, em_idiv_ex),
};
static const struct opcode group4[] = {
@@ -4518,9 +4516,12 @@ static int fastop(struct x86_emulate_ctxt *ctxt, void
(*fop)(struct fastop *))
if (!(ctxt->d & ByteOp))
fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
- : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags)
- : "c"(ctxt->src2.val), [fastop]"S"(fop));
+ : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
+ [fastop]"+S"(fop)
+ : "c"(ctxt->src2.val));
ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);
+ if (!fop)
+ return emulate_de(ctxt);
return X86EMUL_CONTINUE;
}
--
1.8.1.2
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