Jason Wang
2021-Mar-16 07:18 UTC
[RFC v2 05/13] vhost: Route guest->host notification through shadow virtqueue
? 2021/3/16 ??3:48, Eugenio P?rez ??:> Shadow virtqueue notifications forwarding is disabled when vhost_dev > stops, so code flow follows usual cleanup. > > Signed-off-by: Eugenio P?rez <eperezma at redhat.com> > --- > hw/virtio/vhost-shadow-virtqueue.h | 7 ++ > include/hw/virtio/vhost.h | 4 + > hw/virtio/vhost-shadow-virtqueue.c | 113 ++++++++++++++++++++++- > hw/virtio/vhost.c | 143 ++++++++++++++++++++++++++++- > 4 files changed, 265 insertions(+), 2 deletions(-) > > diff --git a/hw/virtio/vhost-shadow-virtqueue.h b/hw/virtio/vhost-shadow-virtqueue.h > index 6cc18d6acb..c891c6510d 100644 > --- a/hw/virtio/vhost-shadow-virtqueue.h > +++ b/hw/virtio/vhost-shadow-virtqueue.h > @@ -17,6 +17,13 @@ > > typedef struct VhostShadowVirtqueue VhostShadowVirtqueue; > > +bool vhost_shadow_vq_start(struct vhost_dev *dev, > + unsigned idx, > + VhostShadowVirtqueue *svq); > +void vhost_shadow_vq_stop(struct vhost_dev *dev, > + unsigned idx, > + VhostShadowVirtqueue *svq); > + > VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx); > > void vhost_shadow_vq_free(VhostShadowVirtqueue *vq); > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h > index ac963bf23d..7ffdf9aea0 100644 > --- a/include/hw/virtio/vhost.h > +++ b/include/hw/virtio/vhost.h > @@ -55,6 +55,8 @@ struct vhost_iommu { > QLIST_ENTRY(vhost_iommu) iommu_next; > }; > > +typedef struct VhostShadowVirtqueue VhostShadowVirtqueue; > + > typedef struct VhostDevConfigOps { > /* Vhost device config space changed callback > */ > @@ -83,7 +85,9 @@ struct vhost_dev { > uint64_t backend_cap; > bool started; > bool log_enabled; > + bool shadow_vqs_enabled; > uint64_t log_size; > + VhostShadowVirtqueue **shadow_vqs;Any reason that you don't embed the shadow virtqueue into vhost_virtqueue structure? (Note that there's a masked_notifier in struct vhost_virtqueue).> Error *migration_blocker; > const VhostOps *vhost_ops; > void *opaque; > diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c > index 4512e5b058..3e43399e9c 100644 > --- a/hw/virtio/vhost-shadow-virtqueue.c > +++ b/hw/virtio/vhost-shadow-virtqueue.c > @@ -8,9 +8,12 @@ > */ > > #include "hw/virtio/vhost-shadow-virtqueue.h" > +#include "hw/virtio/vhost.h" > + > +#include "standard-headers/linux/vhost_types.h" > > #include "qemu/error-report.h" > -#include "qemu/event_notifier.h" > +#include "qemu/main-loop.h" > > /* Shadow virtqueue to relay notifications */ > typedef struct VhostShadowVirtqueue { > @@ -18,14 +21,121 @@ typedef struct VhostShadowVirtqueue { > EventNotifier kick_notifier; > /* Shadow call notifier, sent to vhost */ > EventNotifier call_notifier; > + > + /* > + * Borrowed virtqueue's guest to host notifier. > + * To borrow it in this event notifier allows to register on the event > + * loop and access the associated shadow virtqueue easily. If we use the > + * VirtQueue, we don't have an easy way to retrieve it.So this is something that worries me. It looks like a layer violation that makes the codes harder to work correctly. I wonder if it would be simpler to start from a vDPA dedicated shadow virtqueue implementation: 1) have the above fields embeded in vhost_vdpa structure 2) Work at the level of vhost_vdpa_set_vring_kick()/vhost_vdpa_set_vring_call() Then the layer is still isolated and you have a much simpler context to work that you don't need to care a lot of synchornization: 1) vq masking 2) vhost dev start and stop ?> + * > + * So shadow virtqueue must not clean it, or we would lose VirtQueue one. > + */ > + EventNotifier host_notifier; > + > + /* Virtio queue shadowing */ > + VirtQueue *vq; > } VhostShadowVirtqueue; > > +/* Forward guest notifications */ > +static void vhost_handle_guest_kick(EventNotifier *n) > +{ > + VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue, > + host_notifier); > + > + if (unlikely(!event_notifier_test_and_clear(n))) { > + return; > + } > + > + event_notifier_set(&svq->kick_notifier); > +} > + > +/* > + * Restore the vhost guest to host notifier, i.e., disables svq effect. > + */ > +static int vhost_shadow_vq_restore_vdev_host_notifier(struct vhost_dev *dev, > + unsigned vhost_index, > + VhostShadowVirtqueue *svq) > +{ > + EventNotifier *vq_host_notifier = virtio_queue_get_host_notifier(svq->vq); > + struct vhost_vring_file file = { > + .index = vhost_index, > + .fd = event_notifier_get_fd(vq_host_notifier), > + }; > + int r; > + > + /* Restore vhost kick */ > + r = dev->vhost_ops->vhost_set_vring_kick(dev, &file); > + return r ? -errno : 0; > +} > + > +/* > + * Start shadow virtqueue operation. > + * @dev vhost device > + * @hidx vhost virtqueue index > + * @svq Shadow Virtqueue > + */ > +bool vhost_shadow_vq_start(struct vhost_dev *dev, > + unsigned idx, > + VhostShadowVirtqueue *svq)It looks to me this assumes the vhost_dev is started before vhost_shadow_vq_start()?> +{ > + EventNotifier *vq_host_notifier = virtio_queue_get_host_notifier(svq->vq); > + struct vhost_vring_file file = { > + .index = idx, > + .fd = event_notifier_get_fd(&svq->kick_notifier), > + }; > + int r; > + > + /* Check that notifications are still going directly to vhost dev */ > + assert(virtio_queue_is_host_notifier_enabled(svq->vq)); > + > + /* > + * event_notifier_set_handler already checks for guest's notifications if > + * they arrive in the switch, so there is no need to explicitely check for > + * them. > + */ > + event_notifier_init_fd(&svq->host_notifier, > + event_notifier_get_fd(vq_host_notifier)); > + event_notifier_set_handler(&svq->host_notifier, vhost_handle_guest_kick); > + > + r = dev->vhost_ops->vhost_set_vring_kick(dev, &file); > + if (unlikely(r != 0)) { > + error_report("Couldn't set kick fd: %s", strerror(errno)); > + goto err_set_vring_kick; > + } > + > + return true; > + > +err_set_vring_kick: > + event_notifier_set_handler(&svq->host_notifier, NULL); > + > + return false; > +} > + > +/* > + * Stop shadow virtqueue operation. > + * @dev vhost device > + * @idx vhost queue index > + * @svq Shadow Virtqueue > + */ > +void vhost_shadow_vq_stop(struct vhost_dev *dev, > + unsigned idx, > + VhostShadowVirtqueue *svq) > +{ > + int r = vhost_shadow_vq_restore_vdev_host_notifier(dev, idx, svq); > + if (unlikely(r < 0)) { > + error_report("Couldn't restore vq kick fd: %s", strerror(-r)); > + } > + > + event_notifier_set_handler(&svq->host_notifier, NULL); > +} > + > /* > * Creates vhost shadow virtqueue, and instruct vhost device to use the shadow > * methods and file descriptors. > */ > VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx) > { > + int vq_idx = dev->vq_index + idx; > g_autofree VhostShadowVirtqueue *svq = g_new0(VhostShadowVirtqueue, 1); > int r; > > @@ -43,6 +153,7 @@ VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx) > goto err_init_call_notifier; > } > > + svq->vq = virtio_get_queue(dev->vdev, vq_idx); > return g_steal_pointer(&svq); > > err_init_call_notifier: > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index 97f1bcfa42..4858a35df6 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -25,6 +25,7 @@ > #include "exec/address-spaces.h" > #include "hw/virtio/virtio-bus.h" > #include "hw/virtio/virtio-access.h" > +#include "hw/virtio/vhost-shadow-virtqueue.h" > #include "migration/blocker.h" > #include "migration/qemu-file-types.h" > #include "sysemu/dma.h" > @@ -1219,6 +1220,74 @@ static void vhost_virtqueue_stop(struct vhost_dev *dev, > 0, virtio_queue_get_desc_size(vdev, idx)); > } > > +static int vhost_sw_live_migration_stop(struct vhost_dev *dev) > +{ > + int idx; > + > + dev->shadow_vqs_enabled = false; > + > + for (idx = 0; idx < dev->nvqs; ++idx) { > + vhost_shadow_vq_stop(dev, idx, dev->shadow_vqs[idx]); > + vhost_shadow_vq_free(dev->shadow_vqs[idx]); > + } > + > + g_free(dev->shadow_vqs); > + dev->shadow_vqs = NULL; > + return 0; > +} > + > +static int vhost_sw_live_migration_start(struct vhost_dev *dev) > +{ > + int idx, stop_idx; > + > + dev->shadow_vqs = g_new0(VhostShadowVirtqueue *, dev->nvqs); > + for (idx = 0; idx < dev->nvqs; ++idx) { > + dev->shadow_vqs[idx] = vhost_shadow_vq_new(dev, idx); > + if (unlikely(dev->shadow_vqs[idx] == NULL)) { > + goto err_new; > + } > + } > + > + dev->shadow_vqs_enabled = true; > + for (idx = 0; idx < dev->nvqs; ++idx) { > + bool ok = vhost_shadow_vq_start(dev, idx, dev->shadow_vqs[idx]); > + if (unlikely(!ok)) { > + goto err_start; > + } > + } > + > + return 0; > + > +err_start: > + dev->shadow_vqs_enabled = false; > + for (stop_idx = 0; stop_idx < idx; stop_idx++) { > + vhost_shadow_vq_stop(dev, idx, dev->shadow_vqs[stop_idx]); > + } > + > +err_new: > + for (idx = 0; idx < dev->nvqs; ++idx) { > + vhost_shadow_vq_free(dev->shadow_vqs[idx]); > + } > + g_free(dev->shadow_vqs); > + > + return -1; > +} > + > +static int vhost_sw_live_migration_enable(struct vhost_dev *dev, > + bool enable_lm) > +{So the live migration part should be done in an separted patch. Thanks> + int r; > + > + if (enable_lm == dev->shadow_vqs_enabled) { > + return 0; > + } > + > + r = enable_lm ? vhost_sw_live_migration_start(dev) > + : vhost_sw_live_migration_stop(dev); > + > + return r; > +} > + > static void vhost_eventfd_add(MemoryListener *listener, > MemoryRegionSection *section, > bool match_data, uint64_t data, EventNotifier *e) > @@ -1381,6 +1450,7 @@ int vhost_dev_init(struct vhost_dev *hdev, void *opaque, > hdev->log = NULL; > hdev->log_size = 0; > hdev->log_enabled = false; > + hdev->shadow_vqs_enabled = false; > hdev->started = false; > memory_listener_register(&hdev->memory_listener, &address_space_memory); > QLIST_INSERT_HEAD(&vhost_devices, hdev, entry); > @@ -1484,6 +1554,10 @@ void vhost_dev_disable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev) > BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev))); > int i, r; > > + if (hdev->shadow_vqs_enabled) { > + vhost_sw_live_migration_enable(hdev, false); > + } > + > for (i = 0; i < hdev->nvqs; ++i) { > r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + i, > false); > @@ -1798,6 +1872,7 @@ fail_features: > void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev) > { > int i; > + bool is_shadow_vqs_enabled = hdev->shadow_vqs_enabled; > > /* should only be called after backend is connected */ > assert(hdev->vhost_ops); > @@ -1805,7 +1880,16 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev) > if (hdev->vhost_ops->vhost_dev_start) { > hdev->vhost_ops->vhost_dev_start(hdev, false); > } > + if (is_shadow_vqs_enabled) { > + /* Shadow virtqueue will be stopped */ > + hdev->shadow_vqs_enabled = false; > + } > for (i = 0; i < hdev->nvqs; ++i) { > + if (is_shadow_vqs_enabled) { > + vhost_shadow_vq_stop(hdev, i, hdev->shadow_vqs[i]); > + vhost_shadow_vq_free(hdev->shadow_vqs[i]); > + } > + > vhost_virtqueue_stop(hdev, > vdev, > hdev->vqs + i, > @@ -1819,6 +1903,8 @@ void vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev) > memory_listener_unregister(&hdev->iommu_listener); > } > vhost_log_put(hdev, true); > + g_free(hdev->shadow_vqs); > + hdev->shadow_vqs_enabled = false; > hdev->started = false; > hdev->vdev = NULL; > } > @@ -1835,5 +1921,60 @@ int vhost_net_set_backend(struct vhost_dev *hdev, > > void qmp_x_vhost_enable_shadow_vq(const char *name, bool enable, Error **errp) > { > - error_setg(errp, "Shadow virtqueue still not implemented"); > + struct vhost_dev *hdev, *hdev_err; > + VirtIODevice *vdev; > + const char *err_cause = NULL; > + int r; > + ErrorClass err_class = ERROR_CLASS_GENERIC_ERROR; > + > + QLIST_FOREACH(hdev, &vhost_devices, entry) { > + if (hdev->vdev && 0 == strcmp(hdev->vdev->name, name)) { > + vdev = hdev->vdev; > + break; > + } > + } > + > + if (!hdev) { > + err_class = ERROR_CLASS_DEVICE_NOT_FOUND; > + err_cause = "Device not found"; > + goto not_found_err; > + } > + > + for ( ; hdev; hdev = QLIST_NEXT(hdev, entry)) { > + if (vdev != hdev->vdev) { > + continue; > + } > + > + if (!hdev->started) { > + err_cause = "Device is not started"; > + goto err; > + } > + > + r = vhost_sw_live_migration_enable(hdev, enable); > + if (unlikely(r)) { > + err_cause = "Error enabling (see monitor)"; > + goto err; > + } > + } > + > + return; > + > +err: > + QLIST_FOREACH(hdev_err, &vhost_devices, entry) { > + if (hdev_err == hdev) { > + break; > + } > + > + if (vdev != hdev->vdev) { > + continue; > + } > + > + vhost_sw_live_migration_enable(hdev, !enable); > + } > + > +not_found_err: > + if (err_cause) { > + error_set(errp, err_class, > + "Can't enable shadow vq on %s: %s", name, err_cause); > + } > }