EFLAGS.ZF needs to be checked after each iteration, not before.
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
---
v3: if restarting an instruction, don't advance rip
arch/x86/kvm/emulate.c | 41 ++++++++++++++++++++---------------------
1 files changed, 20 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 729853a..4372dc5 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2782,28 +2782,10 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
ctxt->restart = true;
/* All REP prefixes have the same first termination condition */
if (address_mask(c, c->regs[VCPU_REGS_RCX]) == 0) {
- string_done:
ctxt->restart = false;
ctxt->eip = c->eip;
goto done;
}
- /* The second termination condition only applies for REPE
- * and REPNE. Test if the repeat string operation prefix is
- * REPE/REPZ or REPNE/REPNZ and if it's the case it tests the
- * corresponding termination condition according to:
- * - if REPE/REPZ and ZF = 0 then done
- * - if REPNE/REPNZ and ZF = 1 then done
- */
- if ((c->b == 0xa6) || (c->b == 0xa7) ||
- (c->b == 0xae) || (c->b == 0xaf)) {
- if ((c->rep_prefix == REPE_PREFIX) &&
- ((ctxt->eflags & EFLG_ZF) == 0))
- goto string_done;
- if ((c->rep_prefix == REPNE_PREFIX) &&
- ((ctxt->eflags & EFLG_ZF) == EFLG_ZF))
- goto string_done;
- }
- c->eip = ctxt->eip;
}
if ((c->src.type == OP_MEM) && !(c->d & NoAccess)) {
@@ -3230,20 +3212,37 @@ writeback:
if (c->rep_prefix && (c->d & String)) {
struct read_cache *rc = &ctxt->decode.io_read;
register_address_increment(c, &c->regs[VCPU_REGS_RCX], -1);
+ /* The second termination condition only applies for REPE
+ * and REPNE. Test if the repeat string operation prefix is
+ * REPE/REPZ or REPNE/REPNZ and if it's the case it tests the
+ * corresponding termination condition according to:
+ * - if REPE/REPZ and ZF = 0 then done
+ * - if REPNE/REPNZ and ZF = 1 then done
+ */
+ if (((c->b == 0xa6) || (c->b == 0xa7) ||
+ (c->b == 0xae) || (c->b == 0xaf))
+ && (((c->rep_prefix == REPE_PREFIX) &&
+ ((ctxt->eflags & EFLG_ZF) == 0))
+ || ((c->rep_prefix == REPNE_PREFIX) &&
+ ((ctxt->eflags & EFLG_ZF) == EFLG_ZF))))
+ ctxt->restart = false;
/*
* Re-enter guest when pio read ahead buffer is empty or,
* if it is not used, after each 1024 iteration.
*/
- if ((rc->end == 0 && !(c->regs[VCPU_REGS_RCX] & 0x3ff)) ||
- (rc->end != 0 && rc->end == rc->pos))
+ else if ((rc->end == 0 && !(c->regs[VCPU_REGS_RCX] & 0x3ff)) ||
+ (rc->end != 0 && rc->end == rc->pos)) {
ctxt->restart = false;
+ c->eip = ctxt->eip;
+ }
}
/*
* reset read cache here in case string instruction is restared
* without decoding
*/
ctxt->decode.mem_read.end = 0;
- ctxt->eip = c->eip;
+ if (!ctxt->restart)
+ ctxt->eip = c->eip;
done:
return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
--
1.7.1
--
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