> 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?
>
It broken the boot from cdrom, even emulate_invalid_guest_state=0
#qemu-system-x86_64 --boot d --cdrom fdbasews.iso
This will return can not boot from CDROM.
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