On 08/19/2010 07:55 AM, Wei Yongjun wrote:
> Hi Avi Kivity:
>
>> EFLAGS.ZF needs to be checked after each iteration, not before.
>>
>> Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
>> ---
>> arch/x86/kvm/emulate.c | 38 ++++++++++++++++++--------------------
>> 1 files changed, 18 insertions(+), 20 deletions(-)
>>
>> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
>> index 729853a..d15a746 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;
>>
> It seems that you cannot remove the above line, the assign for eip is need.
> remove it will break FreeDOS livecd. Not sure why need this.
I'll try it out. Are you running FreeDOS with
emulate_invalid_guest_state=0 or 1?
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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