> -----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. 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
