From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH v3] KVM: x86 emulator: fix REPZ/REPNZ termination condition Date: Thu, 19 Aug 2010 15:14:15 +0300 Message-ID: <4C6D2017.5000500@redhat.com> References: <1282217648-3844-1-git-send-email-avi@redhat.com> <20100819120921.GJ10499@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , kvm@vger.kernel.org, Wei Yongjun To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:12725 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751943Ab0HSMOT (ORCPT ); Thu, 19 Aug 2010 08:14:19 -0400 In-Reply-To: <20100819120921.GJ10499@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/19/2010 03:09 PM, Gleb Natapov wrote: > On Thu, Aug 19, 2010 at 02:34:08PM +0300, Avi Kivity wrote: >> EFLAGS.ZF needs to be checked after each iteration, not before. >> >> Signed-off-by: Avi Kivity >> --- >> >> 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; >> > We will advance rip past instruction if exception is generated during > instruction emulation. Consequently exception will be injected at the > wrong rip. I think we should try different approach to fix this problem. Yes, I agree. It's too confusing. -- error compiling committee.c: too many arguments to function