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([2a01:e0a:165:d60:266c:b13b:afd7:40fd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5e8e1e285sm17554358f8f.76.2025.07.16.05.53.29 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 16 Jul 2025 05:53:29 -0700 (PDT) Message-ID: <9ad2be7c-5399-4a7e-98c2-badb44f64145@redhat.com> Date: Wed, 16 Jul 2025 14:53:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V1 2/2] vfio/pci: preserve pending interrupts To: Steve Sistare , qemu-devel@nongnu.org Cc: Zhenzhong Duan , Alex Williamson , 'Peter Xu' References: <1752503222-222669-1-git-send-email-steven.sistare@oracle.com> <1752503222-222669-3-git-send-email-steven.sistare@oracle.com> Content-Language: en-US, fr From: =?UTF-8?Q?C=C3=A9dric_Le_Goater?= Autocrypt: addr=clg@redhat.com; keydata= xsFNBFu8o3UBEADP+oJVJaWm5vzZa/iLgpBAuzxSmNYhURZH+guITvSySk30YWfLYGBWQgeo 8NzNXBY3cH7JX3/a0jzmhDc0U61qFxVgrPqs1PQOjp7yRSFuDAnjtRqNvWkvlnRWLFq4+U5t yzYe4SFMjFb6Oc0xkQmaK2flmiJNnnxPttYwKBPd98WfXMmjwAv7QfwW+OL3VlTPADgzkcqj 53bfZ4VblAQrq6Ctbtu7JuUGAxSIL3XqeQlAwwLTfFGrmpY7MroE7n9Rl+hy/kuIrb/TO8n0 ZxYXvvhT7OmRKvbYuc5Jze6o7op/bJHlufY+AquYQ4dPxjPPVUT/DLiUYJ3oVBWFYNbzfOrV RxEwNuRbycttMiZWxgflsQoHF06q/2l4ttS3zsV4TDZudMq0TbCH/uJFPFsbHUN91qwwaN/+ gy1j7o6aWMz+Ib3O9dK2M/j/O/Ube95mdCqN4N/uSnDlca3YDEWrV9jO1mUS/ndOkjxa34ia 70FjwiSQAsyIwqbRO3CGmiOJqDa9qNvd2TJgAaS2WCw/TlBALjVQ7AyoPEoBPj31K74Wc4GS Rm+FSch32ei61yFu6ACdZ12i5Edt+To+hkElzjt6db/UgRUeKfzlMB7PodK7o8NBD8outJGS tsL2GRX24QvvBuusJdMiLGpNz3uqyqwzC5w0Fd34E6G94806fwARAQABzSJDw6lkcmljIExl IEdvYXRlciA8Y2xnQHJlZGhhdC5jb20+wsGRBBMBCAA7FiEEoPZlSPBIlev+awtgUaNDx8/7 7KEFAmTLlVECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgkQUaNDx8/77KG0eg// S0zIzTcxkrwJ/9XgdcvVTnXLVF9V4/tZPfB7sCp8rpDCEseU6O0TkOVFoGWM39sEMiQBSvyY lHrP7p7E/JYQNNLh441MfaX8RJ5Ul3btluLapm8oHp/vbHKV2IhLcpNCfAqaQKdfk8yazYhh EdxTBlzxPcu+78uE5fF4wusmtutK0JG0sAgq0mHFZX7qKG6LIbdLdaQalZ8CCFMKUhLptW71 xe+aNrn7hScBoOj2kTDRgf9CE7svmjGToJzUxgeh9mIkxAxTu7XU+8lmL28j2L5uNuDOq9vl hM30OT+pfHmyPLtLK8+GXfFDxjea5hZLF+2yolE/ATQFt9AmOmXC+YayrcO2ZvdnKExZS1o8 VUKpZgRnkwMUUReaF/mTauRQGLuS4lDcI4DrARPyLGNbvYlpmJWnGRWCDguQ/LBPpbG7djoy k3NlvoeA757c4DgCzggViqLm0Bae320qEc6z9o0X0ePqSU2f7vcuWN49Uhox5kM5L86DzjEQ RHXndoJkeL8LmHx8DM+kx4aZt0zVfCHwmKTkSTQoAQakLpLte7tWXIio9ZKhUGPv/eHxXEoS 0rOOAZ6np1U/xNR82QbF9qr9TrTVI3GtVe7Vxmff+qoSAxJiZQCo5kt0YlWwti2fFI4xvkOi V7lyhOA3+/3oRKpZYQ86Frlo61HU3r6d9wzOwU0EW7yjdQEQALyDNNMw/08/fsyWEWjfqVhW pOOrX2h+z4q0lOHkjxi/FRIRLfXeZjFfNQNLSoL8j1y2rQOs1j1g+NV3K5hrZYYcMs0xhmrZ KXAHjjDx7FW3sG3jcGjFW5Xk4olTrZwFsZVUcP8XZlArLmkAX3UyrrXEWPSBJCXxDIW1hzwp bV/nVbo/K9XBptT/wPd+RPiOTIIRptjypGY+S23HYBDND3mtfTz/uY0Jytaio9GETj+fFis6 TxFjjbZNUxKpwftu/4RimZ7qL+uM1rG1lLWc9SPtFxRQ8uLvLOUFB1AqHixBcx7LIXSKZEFU CSLB2AE4wXQkJbApye48qnZ09zc929df5gU6hjgqV9Gk1rIfHxvTsYltA1jWalySEScmr0iS YBZjw8Nbd7SxeomAxzBv2l1Fk8fPzR7M616dtb3Z3HLjyvwAwxtfGD7VnvINPbzyibbe9c6g LxYCr23c2Ry0UfFXh6UKD83d5ybqnXrEJ5n/t1+TLGCYGzF2erVYGkQrReJe8Mld3iGVldB7 JhuAU1+d88NS3aBpNF6TbGXqlXGF6Yua6n1cOY2Yb4lO/mDKgjXd3aviqlwVlodC8AwI0Sdu jWryzL5/AGEU2sIDQCHuv1QgzmKwhE58d475KdVX/3Vt5I9kTXpvEpfW18TjlFkdHGESM/Jx IqVsqvhAJkalABEBAAHCwV8EGAECAAkFAlu8o3UCGwwACgkQUaNDx8/77KEhwg//WqVopd5k 8hQb9VVdk6RQOCTfo6wHhEqgjbXQGlaxKHoXywEQBi8eULbeMQf5l4+tHJWBxswQ93IHBQjK yKyNr4FXseUI5O20XVNYDJZUrhA4yn0e/Af0IX25d94HXQ5sMTWr1qlSK6Zu79lbH3R57w9j hQm9emQEp785ui3A5U2Lqp6nWYWXz0eUZ0Tad2zC71Gg9VazU9MXyWn749s0nXbVLcLS0yop s302Gf3ZmtgfXTX/W+M25hiVRRKCH88yr6it+OMJBUndQVAA/fE9hYom6t/zqA248j0QAV/p LHH3hSirE1mv+7jpQnhMvatrwUpeXrOiEw1nHzWCqOJUZ4SY+HmGFW0YirWV2mYKoaGO2YBU wYF7O9TI3GEEgRMBIRT98fHa0NPwtlTktVISl73LpgVscdW8yg9Gc82oe8FzU1uHjU8b10lU XOMHpqDDEV9//r4ZhkKZ9C4O+YZcTFu+mvAY3GlqivBNkmYsHYSlFsbxc37E1HpTEaSWsGfA HQoPn9qrDJgsgcbBVc1gkUT6hnxShKPp4PlsZVMNjvPAnr5TEBgHkk54HQRhhwcYv1T2QumQ izDiU6iOrUzBThaMhZO3i927SG2DwWDVzZltKrCMD1aMPvb3NU8FOYRhNmIFR3fcalYr+9gD uVKe8BVz4atMOoktmt0GWTOC8P4= In-Reply-To: <1752503222-222669-3-git-send-email-steven.sistare@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.129.124; envelope-from=clg@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org +Peter, for info. On 7/14/25 16:27, Steve Sistare wrote: > cpr-transfer may lose a VFIO interrupt because the KVM instance is > destroyed and recreated. If an interrupt arrives in the middle, it is > dropped. To fix, disable pended interrupts during cpr save, and pick > up the pieces. In more detail: > > Stop the VCPUs. Call kvm_irqchip_remove_irqfd_notifier_gsi --> KVM_IRQFD to > deassign the irqfd gsi that routes interrupts directly to the VCPU and KVM. > After this call, interrupts fall back to the kernel vfio_msihandler, which > writes to QEMU's kvm_interrupt eventfd. CPR already preserves that > eventfd. When the route is re-established in new QEMU, the kernel tests > the eventfd and pends an interrupt to KVM if necessary. > > Deassign INTx in a similar manner. For both MSI and INTx, remove the > eventfd handler so old QEMU does not consume an event. > > If an interrupt was already pended to KVM prior to the completion of > kvm_irqchip_remove_irqfd_notifier_gsi, it will be recovered by the > subsequent call to cpu_synchronize_all_states, which pulls KVM interrupt > state to userland prior to saving it in vmstate. > > Signed-off-by: Steve Sistare > --- > hw/vfio/cpr.c | 90 ++++++++++++++++++++++++++++++++++++++ > hw/vfio/pci.c | 2 + > hw/vfio/pci.h | 1 + > include/hw/vfio/vfio-cpr.h | 6 +++ > 4 files changed, 99 insertions(+) > > diff --git a/hw/vfio/cpr.c b/hw/vfio/cpr.c > index 2a244fc4b6..ae2a6b7acd 100644 > --- a/hw/vfio/cpr.c > +++ b/hw/vfio/cpr.c > @@ -198,3 +198,93 @@ void vfio_cpr_add_kvm_notifier(void) > MIG_MODE_CPR_TRANSFER); > } > } > + > +static int set_irqfd_notifier_gsi(KVMState *s, EventNotifier *n, > + EventNotifier *rn, int virq, bool enable) > +{ > + if (enable) { > + return kvm_irqchip_add_irqfd_notifier_gsi(s, n, rn, virq); > + } else { > + return kvm_irqchip_remove_irqfd_notifier_gsi(s, n, virq); > + } > +} > + > +static int vfio_cpr_set_msi_virq(VFIOPCIDevice *vdev, Error **errp, bool enable) > +{ > + const char *op = (enable ? "enable" : "disable"); > + PCIDevice *pdev = &vdev->pdev; > + int i, nr_vectors, ret = 0; > + > + if (msix_enabled(pdev)) { > + nr_vectors = vdev->msix->entries; > + > + } else if (msi_enabled(pdev)) { > + nr_vectors = msi_nr_vectors_allocated(pdev); > + > + } else if (vfio_pci_read_config(pdev, PCI_INTERRUPT_PIN, 1)) { > + ret = set_irqfd_notifier_gsi(kvm_state, &vdev->intx.interrupt, > + &vdev->intx.unmask, vdev->intx.route.irq, > + enable); > + if (ret) { > + error_setg(errp, "failed to %s INTx irq %d: error %d", > + op, vdev->intx.route.irq, ret); > + } else { > + vfio_pci_intx_set_handler(vdev, enable); > + } > + return ret; > + > + } else { > + nr_vectors = 0; > + } > + > + for (i = 0; i < nr_vectors; i++) { > + VFIOMSIVector *vector = &vdev->msi_vectors[i]; > + if (vector->use) { > + ret = set_irqfd_notifier_gsi(kvm_state, &vector->kvm_interrupt, > + NULL, vector->virq, enable); > + if (ret) { > + error_setg(errp, "failed to %s msi vector %d virq %d: error %d", > + op, i, vector->virq, ret); > + } else { > + vfio_pci_msi_set_handler(vdev, i, enable); > + } > + } > + } > + > + return ret; > +} > + > +/* > + * When CPR starts, detach IRQs from the VFIO device so future interrupts > + * are posted to kvm_interrupt, which is preserved in new QEMU. Interrupts > + * that were already posted to the old KVM instance, but not delivered to the > + * VCPU, are recovered via KVM_GET_LAPIC and pushed to the new KVM instance > + * in new QEMU. > + * > + * If CPR fails, reattach the IRQs. > + */ > +static int vfio_cpr_pci_notifier(NotifierWithReturn *notifier, > + MigrationEvent *e, Error **errp) > +{ > + VFIOPCIDevice *vdev = > + container_of(notifier, VFIOPCIDevice, cpr.transfer_notifier); > + > + if (e->type == MIG_EVENT_PRECOPY_SETUP) { > + return vfio_cpr_set_msi_virq(vdev, errp, false); > + } else if (e->type == MIG_EVENT_PRECOPY_FAILED) { > + return vfio_cpr_set_msi_virq(vdev, errp, true); > + } > + return 0; > +} > + > +void vfio_cpr_pci_register_device(VFIOPCIDevice *vdev) > +{ > + migration_add_notifier_mode(&vdev->cpr.transfer_notifier, > + vfio_cpr_pci_notifier, > + MIG_MODE_CPR_TRANSFER); > +} > + > +void vfio_cpr_pci_unregister_device(VFIOPCIDevice *vdev) > +{ > + migration_remove_notifier(&vdev->cpr.transfer_notifier); > +} > diff --git a/hw/vfio/pci.c b/hw/vfio/pci.c > index 8b471c054a..22a4125131 100644 > --- a/hw/vfio/pci.c > +++ b/hw/vfio/pci.c > @@ -2993,6 +2993,7 @@ void vfio_pci_put_device(VFIOPCIDevice *vdev) > { > vfio_display_finalize(vdev); > vfio_bars_finalize(vdev); > + vfio_cpr_pci_unregister_device(vdev); > g_free(vdev->emulated_config_bits); > g_free(vdev->rom); > /* > @@ -3442,6 +3443,7 @@ static void vfio_pci_realize(PCIDevice *pdev, Error **errp) > vfio_pci_register_err_notifier(vdev); > vfio_pci_register_req_notifier(vdev); > vfio_setup_resetfn_quirk(vdev); > + vfio_cpr_pci_register_device(vdev); > > return; > > diff --git a/hw/vfio/pci.h b/hw/vfio/pci.h > index 80c8fcfa07..7989b94eb3 100644 > --- a/hw/vfio/pci.h > +++ b/hw/vfio/pci.h > @@ -194,6 +194,7 @@ struct VFIOPCIDevice { > bool skip_vsc_check; > VFIODisplay *dpy; > Notifier irqchip_change_notifier; > + VFIOPCICPR cpr; > }; > > /* Use uin32_t for vendor & device so PCI_ANY_ID expands and cannot match hw */ > diff --git a/include/hw/vfio/vfio-cpr.h b/include/hw/vfio/vfio-cpr.h > index 80ad20d216..d37daffbc5 100644 > --- a/include/hw/vfio/vfio-cpr.h > +++ b/include/hw/vfio/vfio-cpr.h > @@ -38,6 +38,10 @@ typedef struct VFIODeviceCPR { > uint32_t ioas_id; > } VFIODeviceCPR; > > +typedef struct VFIOPCICPR { > + NotifierWithReturn transfer_notifier; > +} VFIOPCICPR; > + > bool vfio_legacy_cpr_register_container(struct VFIOContainer *container, > Error **errp); > void vfio_legacy_cpr_unregister_container(struct VFIOContainer *container); > @@ -77,5 +81,7 @@ extern const VMStateDescription vfio_cpr_pci_vmstate; > extern const VMStateDescription vmstate_cpr_vfio_devices; > > void vfio_cpr_add_kvm_notifier(void); > +void vfio_cpr_pci_register_device(struct VFIOPCIDevice *vdev); > +void vfio_cpr_pci_unregister_device(struct VFIOPCIDevice *vdev); > > #endif /* HW_VFIO_VFIO_CPR_H */