Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx> writes: > Hi Bandan, > On Wed, Jul 02, 2014 at 12:27:59PM -0400, Bandan Das wrote: >>Wanpeng Li <wanpeng.li@xxxxxxxxxxxxxxx> writes: >> >>> This patch fix bug https://bugzilla.kernel.org/show_bug.cgi?id=72381 >>I can also reproduce this easily with Linux as L1 by "slowing it down" >>eg. running with ept = 0 >> >>I suggest changing the subject to - >>KVM: nVMX: Fix race that incorrectly injects L1's irq to L2 >> > > Ok, I will fold this to next version. ;-) > >>> If we didn't inject a still-pending event to L1 since nested_run_pending, >>> KVM_REQ_EVENT should be requested after the vmexit in order to inject the >>> event to L1. However, current log blindly request a KVM_REQ_EVENT even if >> >>What's current "log" ? Do you mean current "code" ? >> > > Yeah, it's a typo. I mean "logic". > > [...] >>Also, I am wondering isn't it enough to just do this to avoid this race ? >> >> static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu) >> { >>- return (!to_vmx(vcpu)->nested.nested_run_pending && >>+ return (!is_guest_mode(vcpu) && >>+ !to_vmx(vcpu)->nested.nested_run_pending && >> vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) && >> !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & >> > > I don't think you fix the root cause of the race, and there are two cases which > I concern about your proposal: > > - If there is a special L1 which don't ask to exit on external intrs, you will > lose the intrs which L0 inject to L2. Oh didn't think about that case :), thanks for the pointing this out. It's easy to check this with Xen as L1, I suppose. > - If inject_pending_event fail to inject an intr since the change that you made > in vmx_interrupt_allowed, L0 will request an intr window for L2, however, the > intr is belong to L1. Oh, I thought inject_pending_event has kvm_queue_interrupt only if vmx_interrupt_allowed() returns true so, interrupt will be injected correctly on the next vmexit. Anyway, I am hitting another bug with your patch! Please see my other mail to the list. Thanks! > Regards, > Wanpeng Li > >>Thanks, >>Bandan -- 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
