Gleb Natapov wrote: > On Fri, May 29, 2009 at 06:46:47PM +0200, Jan Kiszka wrote: >> Gleb Natapov wrote: >>> On Fri, May 29, 2009 at 04:52:41PM +0200, Jan Kiszka wrote: >>>> Gleb Natapov wrote: >>>>> On Fri, May 29, 2009 at 10:23:24AM +0200, Jan Kiszka wrote: >>>>>> Hi Gleb, >>>>>> >>>>>> with latest kernel modules, namely beginning with 6bc0a1a235 (Remove >>>>>> irq_pending bitmap), I'm loosing interrupts with upstream's KVM support. >>>>>> After some bisecting, hair-pulling and a bit meditation I added a >>>>>> WARN_ON(kvm_cpu_has_interrupt(vcpu)) to kvm_vcpu_ioctl_interrupt, and it >>>>>> actually triggered right before the guest got stuck. >>>>>> >>>>>> This didn't trigger with qemu-kvm (and -no-kvm-irqchip) yet but, on the >>>>>> other hand, I currently do not see a potential bug in upstream's >>>>>> kvm_arch_pre_run. Could you have a look if you can reproduce, >>>>>> specifically if this isn't a KVM kernel issue in the end? >>>>>> >>>>> In kvm_cpu_exec() after calling kvm_arch_pre_run() env->exit_request is >>>>> tested and function can exit without calling kvm_vcpu_ioctl(KVM_RUN). >>>>> Can you check if this what happens in your case? >>>> This path is executed quite frequently here. No obvious correlation with >>>> the lost IRQ. >>>> >>> If kvm_arch_pre_run() injected interrupt kvm_vcpu_ioctl(KVM_RUN) have to >>> be executed before injecting another interrupt, so if on the fist call >>> of kvm_cpu_exec() kvm_arch_pre_run() injected interrupt, but >>> kvm_vcpu_ioctl(KVM_RUN) was not executed because of env->exit_request >>> and on the next kvm_cpu_exec() other interrupt is injected the previous >>> one will be lost. >> ...and kvm_run->ready_for_interrupt_injection is not updated either in >> that case, right? That makes be wonder if KVM_INTERRUPT shouldn't better >> return an error in case the queue is full already. >> > If kvm_vcpu_ioctl(KVM_RUN) is called, but exit happens before interrupt > is injected kvm_run->ready_for_interrupt_injection should be update to > reflect that fact. Yes, but in this case it isn't called if IIUC. So that is the problem upstream KVM faces? Then again: What do you think is the proper long-term fix? Only adjusting upstream KVM (required anyway) or also making the kernel support more robust against this pattern? Jan -- Siemens AG, Corporate Technology, CT SE 2 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
