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Date: Fri, 19 Jan 2018 21:51:40 +0800
From: Yuanhan Liu <yliu@fridaylinux.org>
To: Victor Kaplansky <victork@redhat.com>
Cc: dev@dpdk.org, stable@dpdk.org, Jens Freimann <jfreiman@redhat.com>,
Maxime Coquelin <maxime.coquelin@redhat.com>,
Tiwei Bie <tiwei.bie@intel.com>, "Tan, Jianfeng" <jianfeng.tan@intel.com>,
Stephen Hemminger <stephen@networkplumber.org>
Message-ID: <20180119135140.GO29540@yliu-mob>
References: <20180117154925-mutt-send-email-victork@redhat.com>
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User-Agent: Mutt/1.5.24 (2015-08-30)
Subject: Re: [dpdk-stable] [PATCH v5] vhost_user: protect active rings from
async ring changes
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On Wed, Jan 17, 2018 at 03:49:25PM +0200, Victor Kaplansky wrote:
> 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.
Applied to dpdk-next-virtio, with
Cc: stable@dpdk.org
Thanks.
--yliu
>
> 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 <victork@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