Jason Wang
2021-Mar-16 08:15 UTC
[RFC v2 11/13] vhost: Shadow virtqueue buffers forwarding
? 2021/3/16 ??3:48, Eugenio P?rez ??:> Initial version of shadow virtqueue that actually forward buffers. > > It reuses the VirtQueue code for the device part. The driver part is > based on Linux's virtio_ring driver, but with stripped functionality > and optimizations so it's easier to review. > > These will be added in later commits. > > Signed-off-by: Eugenio P?rez <eperezma at redhat.com> > --- > hw/virtio/vhost-shadow-virtqueue.c | 212 +++++++++++++++++++++++++++-- > hw/virtio/vhost.c | 113 ++++++++++++++- > 2 files changed, 312 insertions(+), 13 deletions(-) > > diff --git a/hw/virtio/vhost-shadow-virtqueue.c b/hw/virtio/vhost-shadow-virtqueue.c > index 1460d1d5d1..68ed0f2740 100644 > --- a/hw/virtio/vhost-shadow-virtqueue.c > +++ b/hw/virtio/vhost-shadow-virtqueue.c > @@ -9,6 +9,7 @@ > > #include "hw/virtio/vhost-shadow-virtqueue.h" > #include "hw/virtio/vhost.h" > +#include "hw/virtio/virtio-access.h" > > #include "standard-headers/linux/vhost_types.h" > > @@ -55,11 +56,96 @@ typedef struct VhostShadowVirtqueue { > /* Virtio device */ > VirtIODevice *vdev; > > + /* Map for returning guest's descriptors */ > + VirtQueueElement **ring_id_maps; > + > + /* Next head to expose to device */ > + uint16_t avail_idx_shadow; > + > + /* Next free descriptor */ > + uint16_t free_head; > + > + /* Last seen used idx */ > + uint16_t shadow_used_idx; > + > + /* Next head to consume from device */ > + uint16_t used_idx; > + > /* Descriptors copied from guest */ > vring_desc_t descs[]; > } VhostShadowVirtqueue; > > -/* Forward guest notifications */ > +static void vhost_vring_write_descs(VhostShadowVirtqueue *svq, > + const struct iovec *iovec, > + size_t num, bool more_descs, bool write) > +{ > + uint16_t i = svq->free_head, last = svq->free_head; > + unsigned n; > + uint16_t flags = write ? virtio_tswap16(svq->vdev, VRING_DESC_F_WRITE) : 0; > + vring_desc_t *descs = svq->vring.desc; > + > + if (num == 0) { > + return; > + } > + > + for (n = 0; n < num; n++) { > + if (more_descs || (n + 1 < num)) { > + descs[i].flags = flags | virtio_tswap16(svq->vdev, > + VRING_DESC_F_NEXT); > + } else { > + descs[i].flags = flags; > + } > + descs[i].addr = virtio_tswap64(svq->vdev, (hwaddr)iovec[n].iov_base);So unsing virtio_tswap() is probably not correct since we're talking with vhost backends which has its own endiness. For vhost-vDPA, we can assume that it's a 1.0 device.> + descs[i].len = virtio_tswap32(svq->vdev, iovec[n].iov_len); > + > + last = i; > + i = virtio_tswap16(svq->vdev, descs[i].next); > + } > + > + svq->free_head = virtio_tswap16(svq->vdev, descs[last].next); > +} > + > +static unsigned vhost_shadow_vq_add_split(VhostShadowVirtqueue *svq, > + VirtQueueElement *elem) > +{ > + int head; > + unsigned avail_idx; > + vring_avail_t *avail = svq->vring.avail; > + > + head = svq->free_head; > + > + /* We need some descriptors here */ > + assert(elem->out_num || elem->in_num); > + > + vhost_vring_write_descs(svq, elem->out_sg, elem->out_num, > + elem->in_num > 0, false); > + vhost_vring_write_descs(svq, elem->in_sg, elem->in_num, false, true); > + > + /* > + * Put entry in available array (but don't update avail->idx until they > + * do sync). > + */ > + avail_idx = svq->avail_idx_shadow & (svq->vring.num - 1); > + avail->ring[avail_idx] = virtio_tswap16(svq->vdev, head); > + svq->avail_idx_shadow++; > + > + /* Expose descriptors to device */ > + smp_wmb(); > + avail->idx = virtio_tswap16(svq->vdev, svq->avail_idx_shadow); > + > + return head; > + > +} > + > +static void vhost_shadow_vq_add(VhostShadowVirtqueue *svq, > + VirtQueueElement *elem) > +{ > + unsigned qemu_head = vhost_shadow_vq_add_split(svq, elem); > + > + svq->ring_id_maps[qemu_head] = elem; > +} > + > +/* Handle guest->device notifications */ > static void vhost_handle_guest_kick(EventNotifier *n) > { > VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue, > @@ -69,7 +155,72 @@ static void vhost_handle_guest_kick(EventNotifier *n) > return; > } > > - event_notifier_set(&svq->kick_notifier); > + /* Make available as many buffers as possible */ > + do { > + if (virtio_queue_get_notification(svq->vq)) { > + /* No more notifications until process all available */ > + virtio_queue_set_notification(svq->vq, false); > + } > + > + while (true) { > + VirtQueueElement *elem; > + if (virtio_queue_full(svq->vq)) { > + break;So we've disabled guest notification. If buffer has been consumed, we need to retry the handle_guest_kick here. But I didn't find the code?> + } > + > + elem = virtqueue_pop(svq->vq, sizeof(*elem)); > + if (!elem) { > + break; > + } > + > + vhost_shadow_vq_add(svq, elem); > + event_notifier_set(&svq->kick_notifier); > + } > + > + virtio_queue_set_notification(svq->vq, true); > + } while (!virtio_queue_empty(svq->vq)); > +} > + > +static bool vhost_shadow_vq_more_used(VhostShadowVirtqueue *svq) > +{ > + if (svq->used_idx != svq->shadow_used_idx) { > + return true; > + } > + > + /* Get used idx must not be reordered */ > + smp_rmb(); > + svq->shadow_used_idx = virtio_tswap16(svq->vdev, svq->vring.used->idx); > + > + return svq->used_idx != svq->shadow_used_idx; > +} > + > +static VirtQueueElement *vhost_shadow_vq_get_buf(VhostShadowVirtqueue *svq) > +{ > + vring_desc_t *descs = svq->vring.desc; > + const vring_used_t *used = svq->vring.used; > + vring_used_elem_t used_elem; > + uint16_t last_used; > + > + if (!vhost_shadow_vq_more_used(svq)) { > + return NULL; > + } > + > + last_used = svq->used_idx & (svq->vring.num - 1); > + used_elem.id = virtio_tswap32(svq->vdev, used->ring[last_used].id); > + used_elem.len = virtio_tswap32(svq->vdev, used->ring[last_used].len); > + > + if (unlikely(used_elem.id >= svq->vring.num)) { > + error_report("Device %s says index %u is available", svq->vdev->name, > + used_elem.id); > + return NULL; > + } > + > + descs[used_elem.id].next = svq->free_head; > + svq->free_head = used_elem.id; > + > + svq->used_idx++; > + svq->ring_id_maps[used_elem.id]->len = used_elem.len; > + return g_steal_pointer(&svq->ring_id_maps[used_elem.id]); > } > > /* Forward vhost notifications */ > @@ -78,6 +229,7 @@ static void vhost_shadow_vq_handle_call_no_test(EventNotifier *n) > VhostShadowVirtqueue *svq = container_of(n, VhostShadowVirtqueue, > call_notifier); > EventNotifier *masked_notifier; > + VirtQueue *vq = svq->vq; > > /* Signal start of using masked notifier */ > qemu_event_reset(&svq->masked_notifier.is_free); > @@ -86,14 +238,29 @@ static void vhost_shadow_vq_handle_call_no_test(EventNotifier *n) > qemu_event_set(&svq->masked_notifier.is_free); > } > > - if (!masked_notifier) { > - unsigned n = virtio_get_queue_index(svq->vq); > - virtio_queue_invalidate_signalled_used(svq->vdev, n); > - virtio_notify_irqfd(svq->vdev, svq->vq); > - } else if (!svq->masked_notifier.signaled) { > - svq->masked_notifier.signaled = true; > - event_notifier_set(svq->masked_notifier.n); > - } > + /* Make as many buffers as possible used. */ > + do { > + unsigned i = 0; > + > + /* TODO: Use VRING_AVAIL_F_NO_INTERRUPT */ > + while (true) { > + g_autofree VirtQueueElement *elem = vhost_shadow_vq_get_buf(svq); > + if (!elem) { > + break; > + } > + > + assert(i < svq->vring.num); > + virtqueue_fill(vq, elem, elem->len, i++); > + } > + > + virtqueue_flush(vq, i); > + if (!masked_notifier) { > + virtio_notify_irqfd(svq->vdev, svq->vq); > + } else if (!svq->masked_notifier.signaled) { > + svq->masked_notifier.signaled = true; > + event_notifier_set(svq->masked_notifier.n); > + } > + } while (vhost_shadow_vq_more_used(svq)); > > if (masked_notifier) { > /* Signal not using it anymore */ > @@ -103,7 +270,6 @@ static void vhost_shadow_vq_handle_call_no_test(EventNotifier *n) > > static void vhost_shadow_vq_handle_call(EventNotifier *n) > { > - > if (likely(event_notifier_test_and_clear(n))) { > vhost_shadow_vq_handle_call_no_test(n); > } > @@ -254,7 +420,11 @@ void vhost_shadow_vq_stop(struct vhost_dev *dev, > unsigned idx, > VhostShadowVirtqueue *svq) > { > + int i; > int r = vhost_shadow_vq_restore_vdev_host_notifier(dev, idx, svq); > + > + assert(!dev->shadow_vqs_enabled); > + > if (unlikely(r < 0)) { > error_report("Couldn't restore vq kick fd: %s", strerror(-r)); > } > @@ -272,6 +442,18 @@ void vhost_shadow_vq_stop(struct vhost_dev *dev, > /* Restore vhost call */ > vhost_virtqueue_mask(dev, dev->vdev, dev->vq_index + idx, > dev->vqs[idx].notifier_is_masked); > + > + > + for (i = 0; i < svq->vring.num; ++i) { > + g_autofree VirtQueueElement *elem = svq->ring_id_maps[i]; > + /* > + * Although the doc says we must unpop in order, it's ok to unpop > + * everything. > + */ > + if (elem) { > + virtqueue_unpop(svq->vq, elem, elem->len);Shouldn't we need to wait until all pending requests to be drained? Or we may end up duplicated requests? Thanks> + } > + } > } > > /* > @@ -284,7 +466,7 @@ VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx) > unsigned num = virtio_queue_get_num(dev->vdev, vq_idx); > size_t ring_size = vring_size(num, VRING_DESC_ALIGN_SIZE); > g_autofree VhostShadowVirtqueue *svq = g_malloc0(sizeof(*svq) + ring_size); > - int r; > + int r, i; > > r = event_notifier_init(&svq->kick_notifier, 0); > if (r != 0) { > @@ -303,6 +485,11 @@ VhostShadowVirtqueue *vhost_shadow_vq_new(struct vhost_dev *dev, int idx) > vring_init(&svq->vring, num, svq->descs, VRING_DESC_ALIGN_SIZE); > svq->vq = virtio_get_queue(dev->vdev, vq_idx); > svq->vdev = dev->vdev; > + for (i = 0; i < num - 1; i++) { > + svq->descs[i].next = virtio_tswap16(dev->vdev, i + 1); > + } > + > + svq->ring_id_maps = g_new0(VirtQueueElement *, num); > event_notifier_set_handler(&svq->call_notifier, > vhost_shadow_vq_handle_call); > qemu_event_init(&svq->masked_notifier.is_free, true); > @@ -324,5 +511,6 @@ void vhost_shadow_vq_free(VhostShadowVirtqueue *vq) > event_notifier_cleanup(&vq->kick_notifier); > event_notifier_set_handler(&vq->call_notifier, NULL); > event_notifier_cleanup(&vq->call_notifier); > + g_free(vq->ring_id_maps); > g_free(vq); > } > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c > index eab3e334f2..a373999bc4 100644 > --- a/hw/virtio/vhost.c > +++ b/hw/virtio/vhost.c > @@ -1021,6 +1021,19 @@ int vhost_device_iotlb_miss(struct vhost_dev *dev, uint64_t iova, int write) > > trace_vhost_iotlb_miss(dev, 1); > > + if (qatomic_load_acquire(&dev->shadow_vqs_enabled)) { > + uaddr = iova; > + len = 4096; > + ret = vhost_backend_update_device_iotlb(dev, iova, uaddr, len, > + IOMMU_RW); > + if (ret) { > + trace_vhost_iotlb_miss(dev, 2); > + error_report("Fail to update device iotlb"); > + } > + > + return ret; > + } > + > iotlb = address_space_get_iotlb_entry(dev->vdev->dma_as, > iova, write, > MEMTXATTRS_UNSPECIFIED); > @@ -1227,8 +1240,28 @@ static int vhost_sw_live_migration_stop(struct vhost_dev *dev) > /* Can be read by vhost_virtqueue_mask, from vm exit */ > qatomic_store_release(&dev->shadow_vqs_enabled, false); > > + dev->vhost_ops->vhost_set_vring_enable(dev, false); > + if (vhost_backend_invalidate_device_iotlb(dev, 0, -1ULL)) { > + error_report("Fail to invalidate device iotlb"); > + } > + > for (idx = 0; idx < dev->nvqs; ++idx) { > + /* > + * Update used ring information for IOTLB to work correctly, > + * vhost-kernel code requires for this. > + */ > + struct vhost_virtqueue *vq = dev->vqs + idx; > + vhost_device_iotlb_miss(dev, vq->used_phys, true); > + > vhost_shadow_vq_stop(dev, idx, dev->shadow_vqs[idx]); > + vhost_virtqueue_start(dev, dev->vdev, &dev->vqs[idx], > + dev->vq_index + idx); > + } > + > + /* Enable guest's vq vring */ > + dev->vhost_ops->vhost_set_vring_enable(dev, true); > + > + for (idx = 0; idx < dev->nvqs; ++idx) { > vhost_shadow_vq_free(dev->shadow_vqs[idx]); > } > > @@ -1237,6 +1270,59 @@ static int vhost_sw_live_migration_stop(struct vhost_dev *dev) > return 0; > } > > +/* > + * Start shadow virtqueue in a given queue. > + * In failure case, this function leaves queue working as regular vhost mode. > + */ > +static bool vhost_sw_live_migration_start_vq(struct vhost_dev *dev, > + unsigned idx) > +{ > + struct vhost_vring_addr addr = { > + .index = idx, > + }; > + struct vhost_vring_state s = { > + .index = idx, > + }; > + int r; > + bool ok; > + > + vhost_virtqueue_stop(dev, dev->vdev, &dev->vqs[idx], dev->vq_index + idx); > + ok = vhost_shadow_vq_start(dev, idx, dev->shadow_vqs[idx]); > + if (unlikely(!ok)) { > + return false; > + } > + > + /* From this point, vhost_virtqueue_start can reset these changes */ > + vhost_shadow_vq_get_vring_addr(dev->shadow_vqs[idx], &addr); > + r = dev->vhost_ops->vhost_set_vring_addr(dev, &addr); > + if (unlikely(r != 0)) { > + VHOST_OPS_DEBUG("vhost_set_vring_addr for shadow vq failed"); > + goto err; > + } > + > + r = dev->vhost_ops->vhost_set_vring_base(dev, &s); > + if (unlikely(r != 0)) { > + VHOST_OPS_DEBUG("vhost_set_vring_base for shadow vq failed"); > + goto err; > + } > + > + /* > + * Update used ring information for IOTLB to work correctly, > + * vhost-kernel code requires for this. > + */ > + r = vhost_device_iotlb_miss(dev, addr.used_user_addr, true); > + if (unlikely(r != 0)) { > + /* Debug message already printed */ > + goto err; > + } > + > + return true; > + > +err: > + vhost_virtqueue_start(dev, dev->vdev, &dev->vqs[idx], dev->vq_index + idx); > + return false; > +} > + > static int vhost_sw_live_migration_start(struct vhost_dev *dev) > { > int idx, stop_idx; > @@ -1249,24 +1335,35 @@ static int vhost_sw_live_migration_start(struct vhost_dev *dev) > } > } > > + dev->vhost_ops->vhost_set_vring_enable(dev, false); > + if (vhost_backend_invalidate_device_iotlb(dev, 0, -1ULL)) { > + error_report("Fail to invalidate device iotlb"); > + } > + > /* Can be read by vhost_virtqueue_mask, from vm exit */ > qatomic_store_release(&dev->shadow_vqs_enabled, true); > for (idx = 0; idx < dev->nvqs; ++idx) { > - bool ok = vhost_shadow_vq_start(dev, idx, dev->shadow_vqs[idx]); > + bool ok = vhost_sw_live_migration_start_vq(dev, idx); > if (unlikely(!ok)) { > goto err_start; > } > } > > + /* Enable shadow vq vring */ > + dev->vhost_ops->vhost_set_vring_enable(dev, true); > return 0; > > err_start: > qatomic_store_release(&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]); > + vhost_virtqueue_start(dev, dev->vdev, &dev->vqs[idx], > + dev->vq_index + stop_idx); > } > > err_new: > + /* Enable guest's vring */ > + dev->vhost_ops->vhost_set_vring_enable(dev, true); > for (idx = 0; idx < dev->nvqs; ++idx) { > vhost_shadow_vq_free(dev->shadow_vqs[idx]); > } > @@ -1970,6 +2067,20 @@ void qmp_x_vhost_enable_shadow_vq(const char *name, bool enable, Error **errp) > > if (!hdev->started) { > err_cause = "Device is not started"; > + } else if (!vhost_dev_has_iommu(hdev)) { > + err_cause = "Does not support iommu"; > + } else if (hdev->acked_features & BIT_ULL(VIRTIO_F_RING_PACKED)) { > + err_cause = "Is packed"; > + } else if (hdev->acked_features & BIT_ULL(VIRTIO_RING_F_EVENT_IDX)) { > + err_cause = "Have event idx"; > + } else if (hdev->acked_features & > + BIT_ULL(VIRTIO_RING_F_INDIRECT_DESC)) { > + err_cause = "Supports indirect descriptors"; > + } else if (!hdev->vhost_ops->vhost_set_vring_enable) { > + err_cause = "Cannot pause device"; > + } > + > + if (err_cause) { > goto err; > } >