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<avi@xxxxxxxxxx> --- 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 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
