On 07/06/2017 11:33, Gonglei (Arei) wrote: > >> -----Original Message----- >> From: Paolo Bonzini [mailto:paolo.bonzini@xxxxxxxxx] On Behalf Of Paolo >> Bonzini >> Sent: Tuesday, June 06, 2017 6:57 PM >> To: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx >> Cc: longpeng; Huangweidong (C); Gonglei (Arei); wangxin (U); Radim Krčmář >> Subject: [PATCH CFT 0/4] VT-d PI fixes >> >> These should fix, or at least help, the kernel panic reported by Longpeng >> with VT-d posted interrupts. >> >> CONFIG_DEBUG_LIST reports a double add, meaning that pi_pre_block ran >> twice >> without pi_post_block deleting the vCPU from the blocked_on_vcpu list. >> The only possibility that I could think of is that this: >> >> if (!kvm_arch_has_assigned_device(vcpu->kvm) || >> !irq_remapping_cap(IRQ_POSTING_CAP) || >> !kvm_vcpu_apicv_active(vcpu)) >> return; >> >> was false in pi_post_block. In turn, I can only think of hot-unplug as >> the cause of this imbalance, but maybe there is another way to reach it >> just via repeated startup and shutdown. Gonglei reported problems with >> hot-unplug offlist too, so this is a start. >> >> In any case, patch 2 replaces it with a check on vcpu->pre_pcpu. >> A similar change is done in patch 3 to vmx_vcpu_pi_load. I don't >> have hardware easily accessible with VT-d PI, so these patches are >> compile-tested only. I apologize for any stupid mistakes. >> > Hi Paolo, > > We are testing your patch, but maybe need some time to report > the results because it's not an inevitable problem. Of course! I guess it should run for at least a couple days before deeming it fixed. If you didn't find any immediate showstopper bugs, that's already good. :) Paolo > Meanwhile we also try to find a possible scenario of non-hotplugging to > explain the double-add warnings. > > We found that some other VMs start failed before the kernel painc: > > 2017-06-02T12:27:49.972583Z qemu-kvm: -device vfio-pci,host=0b:10.4,id=hostdev0,bus=pci.0,addr=0x5: vfio: error getting device 0000: > 0b:10.4 from group 97: No such device > Verify all devices in group 97 are bound to vfio-<bus> or pci-stub and not already in use > 2017-06-02T12:27:49.975925Z qemu-kvm: -device vfio-pci,host=0b:10.4,id=hostdev0,bus=pci.0,addr=0x5: vfio: failed to get device 0000: > 0b:10.4 > 2017-06-02T12:27:51.246385Z qemu-kvm: -device vfio-pci,host=0b:10.4,id=hostdev0,bus=pci.0,addr=0x5: Device initialization failed > 2017-06-02 12:27:53.628: shutting down, reason=crashed > 2017-06-02 12:30:48.723: shutting down, reason=failed > > But we don't think those failure will cause the unequal of kvm->arch.assigned_device_count > between pi_pre_block and pi_post_block. Am I right? > > Thanks, > -Gonglei > >
