From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 4/4] KVM: x86 emulator: fix REPZ/REPNZ termination condition Date: Tue, 17 Aug 2010 12:20:34 +0300 Message-ID: <4C6A5462.3090705@redhat.com> References: <1282033603-25938-1-git-send-email-avi@redhat.com> <1282033603-25938-5-git-send-email-avi@redhat.com> <20100817091302.GW10499@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Marcelo Tosatti , Mohammed Gamal To: Gleb Natapov Return-path: Received: from mx1.redhat.com ([209.132.183.28]:3715 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751061Ab0HQJUg (ORCPT ); Tue, 17 Aug 2010 05:20:36 -0400 In-Reply-To: <20100817091302.GW10499@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 08/17/2010 12:13 PM, Gleb Natapov wrote: > On Tue, Aug 17, 2010 at 11:26:43AM +0300, Avi Kivity wrote: >> EFLAGS.ZF needs to be checked after each iteration, not before. >> >> Signed-off-by: Avi Kivity >> --- >> arch/x86/kvm/emulate.c | 42 +++++++++++++++++++++++------------------- >> 1 files changed, 23 insertions(+), 19 deletions(-) >> >> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c >> index 0c0ada9..a2edfb1 100644 >> --- a/arch/x86/kvm/emulate.c >> +++ b/arch/x86/kvm/emulate.c >> @@ -2747,6 +2747,7 @@ x86_emulate_insn(struct x86_emulate_ctxt *ctxt) >> int rc = X86EMUL_CONTINUE; >> int saved_dst_type = c->dst.type; >> int irq; /* Used for int 3, int, and into */ >> + ulong old_eip; > Is never used. > Whoops. >> @@ -3250,13 +3234,33 @@ 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)) { >> + trace_printk("c->eip %lx ctxt->eip %lx\n", >> + c->eip, ctxt->eip); >> + if (((c->rep_prefix == REPE_PREFIX)&& >> + ((ctxt->eflags& EFLG_ZF) == 0)) >> + || ((c->rep_prefix == REPNE_PREFIX)&& >> + ((ctxt->eflags& EFLG_ZF) == EFLG_ZF))) { >> + ctxt->restart = false; > Why not jump to string_done label here? It does a 'goto done;' which skips a couple of things. >> + } >> + } >> /* >> * 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)) >> + (rc->end != 0&& rc->end == rc->pos)) { >> ctxt->restart = false; >> + c->eip = ctxt->eip; > We can get here when instruction is completed by above "if", so same > instruction will reexecute once again. Not good. Will redo (and write tests). -- error compiling committee.c: too many arguments to function