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
