Hi May I know why not use trylock also in enqueue path? Cheers JJ
> > When performing live migration or memory hot-plugging, the changes to the > device and vrings made by message handler done independently from vring > usage by PMD threads. > > This causes for example segfaults during live-migration with MQ enable, but > in general virtually any request sent by qemu changing the state of device > can cause problems. > > These patches fixes all above issues by adding a spinlock to every vring and > requiring message handler to start operation only after ensuring that all PMD > threads related to the device are out of critical section accessing the vring > data. > > Each vring has its own lock in order to not create contention between PMD > threads of different vrings and to prevent performance degradation by > scaling queue pair number. > > See https://bugzilla.redhat.com/show_bug.cgi?id=1450680 > > Signed-off-by: Victor Kaplansky <vict...@redhat.com> > --- > v5: > o get rid of spinlock wrapping functions in vhost.h > > v4: > > o moved access_unlock before accessing enable flag and > access_unlock after iommu_unlock consistently. > o cosmetics: removed blank line. > o the access_lock variable moved to be in the same > cache line with enable and access_ok flags. > o dequeue path is now guarded with trylock and returning > zero if unsuccessful. > o GET_VRING_BASE operation is not guarded by access lock > to avoid deadlock with device_destroy. See the comment > in the code. > o Fixed error path exit from enqueue and dequeue carefully > unlocking access and iommu locks as appropriate. > > v3: > o Added locking to enqueue flow. > o Enqueue path guarded as well as dequeue path. > o Changed name of active_lock. > o Added initialization of guarding spinlock. > o Reworked functions skimming over all virt-queues. > o Performance measurements done by Maxime Coquelin shows > no degradation in bandwidth and throughput. > o Spelling. > o Taking lock only on set operations. > o IOMMU messages are not guarded by access lock. > > v2: > o Fixed checkpatch complains. > o Added Signed-off-by. > o Refined placement of guard to exclude IOMMU messages. > o TODO: performance degradation measurement. > > lib/librte_vhost/vhost.h | 6 ++-- > lib/librte_vhost/vhost.c | 1 + > lib/librte_vhost/vhost_user.c | 70 > +++++++++++++++++++++++++++++++++++++++++++ > lib/librte_vhost/virtio_net.c | 28 ++++++++++++++--- > 4 files changed, 99 insertions(+), 6 deletions(-) > > diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h index > 1cc81c17..c8f2a817 100644 > --- a/lib/librte_vhost/vhost.h > +++ b/lib/librte_vhost/vhost.h > @@ -108,12 +108,14 @@ struct vhost_virtqueue { > > /* Backend value to determine if device should started/stopped */ > int backend; > + int enabled; > + int access_ok; > + rte_spinlock_t access_lock; > + > /* Used to notify the guest (trigger interrupt) */ > int callfd; > /* Currently unused as polling mode is enabled */ > int kickfd; > - int enabled; > - int access_ok; > > /* Physical address of used ring, for logging */ > uint64_t log_guest_addr; > diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c index > 4f8b73a0..dcc42fc7 100644 > --- a/lib/librte_vhost/vhost.c > +++ b/lib/librte_vhost/vhost.c > @@ -259,6 +259,7 @@ alloc_vring_queue(struct virtio_net *dev, uint32_t > vring_idx) > > dev->virtqueue[vring_idx] = vq; > init_vring_queue(dev, vring_idx); > + rte_spinlock_init(&vq->access_lock); > > dev->nr_vring += 1; > > diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c > index f4c7ce46..0685d4e7 100644 > --- a/lib/librte_vhost/vhost_user.c > +++ b/lib/librte_vhost/vhost_user.c > @@ -1190,12 +1190,47 @@ > vhost_user_check_and_alloc_queue_pair(struct virtio_net *dev, > VhostUserMsg *msg) > return alloc_vring_queue(dev, vring_idx); } > > +static void > +vhost_user_lock_all_queue_pairs(struct virtio_net *dev) { > + unsigned int i = 0; > + unsigned int vq_num = 0; > + > + while (vq_num < dev->nr_vring) { > + struct vhost_virtqueue *vq = dev->virtqueue[i]; > + > + if (vq) { > + rte_spinlock_lock(&vq->access_lock); > + vq_num++; > + } > + i++; > + } > +} > + > +static void > +vhost_user_unlock_all_queue_pairs(struct virtio_net *dev) { > + unsigned int i = 0; > + unsigned int vq_num = 0; > + > + while (vq_num < dev->nr_vring) { > + struct vhost_virtqueue *vq = dev->virtqueue[i]; > + > + if (vq) { > + rte_spinlock_unlock(&vq->access_lock); > + vq_num++; > + } > + i++; > + } > +} > + > int > vhost_user_msg_handler(int vid, int fd) { > struct virtio_net *dev; > struct VhostUserMsg msg; > int ret; > + int unlock_required = 0; > > dev = get_device(vid); > if (dev == NULL) > @@ -1241,6 +1276,38 @@ vhost_user_msg_handler(int vid, int fd) > return -1; > } > > + /* > + * Note: we don't lock all queues on VHOST_USER_GET_VRING_BASE, > + * since it is sent when virtio stops and device is destroyed. > + * destroy_device waits for queues to be inactive, so it is safe. > + * Otherwise taking the access_lock would cause a dead lock. > + */ > + switch (msg.request.master) { > + case VHOST_USER_SET_FEATURES: > + case VHOST_USER_SET_PROTOCOL_FEATURES: > + case VHOST_USER_SET_OWNER: > + case VHOST_USER_RESET_OWNER: > + case VHOST_USER_SET_MEM_TABLE: > + case VHOST_USER_SET_LOG_BASE: > + case VHOST_USER_SET_LOG_FD: > + case VHOST_USER_SET_VRING_NUM: > + case VHOST_USER_SET_VRING_ADDR: > + case VHOST_USER_SET_VRING_BASE: > + case VHOST_USER_SET_VRING_KICK: > + case VHOST_USER_SET_VRING_CALL: > + case VHOST_USER_SET_VRING_ERR: > + case VHOST_USER_SET_VRING_ENABLE: > + case VHOST_USER_SEND_RARP: > + case VHOST_USER_NET_SET_MTU: > + case VHOST_USER_SET_SLAVE_REQ_FD: > + vhost_user_lock_all_queue_pairs(dev); > + unlock_required = 1; > + break; > + default: > + break; > + > + } > + > switch (msg.request.master) { > case VHOST_USER_GET_FEATURES: > msg.payload.u64 = vhost_user_get_features(dev); @@ -1342,6 > +1409,9 @@ vhost_user_msg_handler(int vid, int fd) > > } > > + if (unlock_required) > + vhost_user_unlock_all_queue_pairs(dev); > + > if (msg.flags & VHOST_USER_NEED_REPLY) { > msg.payload.u64 = !!ret; > msg.size = sizeof(msg.payload.u64); > diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c > index > 6fee16e5..e09a927d 100644 > --- a/lib/librte_vhost/virtio_net.c > +++ b/lib/librte_vhost/virtio_net.c > @@ -44,6 +44,7 @@ > #include <rte_udp.h> > #include <rte_sctp.h> > #include <rte_arp.h> > +#include <rte_spinlock.h> > > #include "iotlb.h" > #include "vhost.h" > @@ -326,8 +327,11 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t > queue_id, > } > > vq = dev->virtqueue[queue_id]; > + > + rte_spinlock_lock(&vq->access_lock); > + > if (unlikely(vq->enabled == 0)) > - return 0; > + goto out_access_unlock; > > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) > vhost_user_iotlb_rd_lock(vq); > @@ -419,6 +423,9 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t > queue_id, > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) > vhost_user_iotlb_rd_unlock(vq); > > +out_access_unlock: > + rte_spinlock_unlock(&vq->access_lock); > + > return count; > } > > @@ -651,8 +658,11 @@ virtio_dev_merge_rx(struct virtio_net *dev, > uint16_t queue_id, > } > > vq = dev->virtqueue[queue_id]; > + > + rte_spinlock_lock(&vq->access_lock); > + > if (unlikely(vq->enabled == 0)) > - return 0; > + goto out_access_unlock; > > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) > vhost_user_iotlb_rd_lock(vq); > @@ -715,6 +725,9 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t > queue_id, > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) > vhost_user_iotlb_rd_unlock(vq); > > +out_access_unlock: > + rte_spinlock_unlock(&vq->access_lock); > + > return pkt_idx; > } > > @@ -1180,9 +1193,13 @@ rte_vhost_dequeue_burst(int vid, uint16_t > queue_id, > } > > vq = dev->virtqueue[queue_id]; > - if (unlikely(vq->enabled == 0)) > + > + if (unlikely(rte_spinlock_trylock(&vq->access_lock) == 0)) > return 0; > > + if (unlikely(vq->enabled == 0)) > + goto out_access_unlock; > + > vq->batch_copy_nb_elems = 0; > > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) @@ > -1240,7 +1257,7 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id, > if (rarp_mbuf == NULL) { > RTE_LOG(ERR, VHOST_DATA, > "Failed to allocate memory for mbuf.\n"); > - return 0; > + goto out; > } > > if (make_rarp_packet(rarp_mbuf, &dev->mac)) { @@ -1356,6 > +1373,9 @@ rte_vhost_dequeue_burst(int vid, uint16_t queue_id, > if (dev->features & (1ULL << VIRTIO_F_IOMMU_PLATFORM)) > vhost_user_iotlb_rd_unlock(vq); > > +out_access_unlock: > + rte_spinlock_unlock(&vq->access_lock); > + > if (unlikely(rarp_mbuf != NULL)) { > /* > * Inject it to the head of "pkts" array, so that switch's mac > -- > Victor
