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KVM: x86 emulator: fix REPZ/REPNZ termination condition

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EFLAGS.ZF needs to be checked after each iteration, not before.

Signed-off-by: Avi Kivity <avi@redhat.com>
This commit is contained in:
Avi Kivity 2010-08-17 11:22:17 +03:00
parent f6b33fc504
commit 0fa6ccbd28
1 changed files with 20 additions and 21 deletions
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41
arch/x86/kvm/emulate.c
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@ -2781,28 +2781,10 @@ 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)) {
@ -3229,20 +3211,37 @@ 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;