On 2014-07-03 07:29, Bandan Das wrote: > 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. Xen most probably intercepts external interrupts, but Jailhouse definitely does not. We also have a unit test for that, but I will likely not expose the issue of lost events. Jan -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux -- 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
