vhost: support event index
Support the new event index feature. When acked, utilize it to reduce the # of interrupts sent to the guest. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Michael S. Tsirkin
Rusty Russell
parent
a5c262c5fd
commit
8ea8cf89e1
@ -144,7 +144,7 @@ static void handle_tx(struct vhost_net *net)
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}
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mutex_lock(&vq->mutex);
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vhost_disable_notify(vq);
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vhost_disable_notify(&net->dev, vq);
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if (wmem < sock->sk->sk_sndbuf / 2)
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tx_poll_stop(net);
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@ -166,8 +166,8 @@ static void handle_tx(struct vhost_net *net)
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set_bit(SOCK_ASYNC_NOSPACE, &sock->flags);
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break;
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}
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if (unlikely(vhost_enable_notify(vq))) {
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vhost_disable_notify(vq);
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if (unlikely(vhost_enable_notify(&net->dev, vq))) {
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vhost_disable_notify(&net->dev, vq);
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continue;
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}
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break;
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@ -315,7 +315,7 @@ static void handle_rx(struct vhost_net *net)
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return;
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mutex_lock(&vq->mutex);
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vhost_disable_notify(vq);
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vhost_disable_notify(&net->dev, vq);
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vhost_hlen = vq->vhost_hlen;
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sock_hlen = vq->sock_hlen;
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@ -334,10 +334,10 @@ static void handle_rx(struct vhost_net *net)
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break;
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/* OK, now we need to know about added descriptors. */
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if (!headcount) {
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if (unlikely(vhost_enable_notify(vq))) {
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if (unlikely(vhost_enable_notify(&net->dev, vq))) {
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/* They have slipped one in as we were
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* doing that: check again. */
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vhost_disable_notify(vq);
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vhost_disable_notify(&net->dev, vq);
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continue;
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}
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/* Nothing new? Wait for eventfd to tell us
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@ -49,7 +49,7 @@ static void handle_vq(struct vhost_test *n)
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return;
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mutex_lock(&vq->mutex);
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vhost_disable_notify(vq);
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vhost_disable_notify(&n->dev, vq);
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for (;;) {
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head = vhost_get_vq_desc(&n->dev, vq, vq->iov,
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@ -61,8 +61,8 @@ static void handle_vq(struct vhost_test *n)
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break;
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/* Nothing new? Wait for eventfd to tell us they refilled. */
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if (head == vq->num) {
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if (unlikely(vhost_enable_notify(vq))) {
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vhost_disable_notify(vq);
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if (unlikely(vhost_enable_notify(&n->dev, vq))) {
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vhost_disable_notify(&n->dev, vq);
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continue;
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}
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break;
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@ -37,6 +37,9 @@ enum {
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VHOST_MEMORY_F_LOG = 0x1,
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};
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#define vhost_used_event(vq) ((u16 __user *)&vq->avail->ring[vq->num])
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#define vhost_avail_event(vq) ((u16 __user *)&vq->used->ring[vq->num])
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static void vhost_poll_func(struct file *file, wait_queue_head_t *wqh,
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poll_table *pt)
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{
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@ -161,6 +164,8 @@ static void vhost_vq_reset(struct vhost_dev *dev,
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vq->last_avail_idx = 0;
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vq->avail_idx = 0;
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vq->last_used_idx = 0;
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vq->signalled_used = 0;
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vq->signalled_used_valid = false;
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vq->used_flags = 0;
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vq->log_used = false;
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vq->log_addr = -1ull;
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@ -489,16 +494,17 @@ static int memory_access_ok(struct vhost_dev *d, struct vhost_memory *mem,
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return 1;
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}
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static int vq_access_ok(unsigned int num,
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static int vq_access_ok(struct vhost_dev *d, unsigned int num,
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struct vring_desc __user *desc,
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struct vring_avail __user *avail,
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struct vring_used __user *used)
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{
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size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
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return access_ok(VERIFY_READ, desc, num * sizeof *desc) &&
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access_ok(VERIFY_READ, avail,
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sizeof *avail + num * sizeof *avail->ring) &&
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sizeof *avail + num * sizeof *avail->ring + s) &&
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access_ok(VERIFY_WRITE, used,
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sizeof *used + num * sizeof *used->ring);
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sizeof *used + num * sizeof *used->ring + s);
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}
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/* Can we log writes? */
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@ -514,9 +520,11 @@ int vhost_log_access_ok(struct vhost_dev *dev)
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/* Verify access for write logging. */
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/* Caller should have vq mutex and device mutex */
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static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
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static int vq_log_access_ok(struct vhost_dev *d, struct vhost_virtqueue *vq,
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void __user *log_base)
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{
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struct vhost_memory *mp;
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size_t s = vhost_has_feature(d, VIRTIO_RING_F_EVENT_IDX) ? 2 : 0;
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mp = rcu_dereference_protected(vq->dev->memory,
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lockdep_is_held(&vq->mutex));
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@ -524,15 +532,15 @@ static int vq_log_access_ok(struct vhost_virtqueue *vq, void __user *log_base)
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vhost_has_feature(vq->dev, VHOST_F_LOG_ALL)) &&
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(!vq->log_used || log_access_ok(log_base, vq->log_addr,
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sizeof *vq->used +
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vq->num * sizeof *vq->used->ring));
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vq->num * sizeof *vq->used->ring + s));
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}
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/* Can we start vq? */
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/* Caller should have vq mutex and device mutex */
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int vhost_vq_access_ok(struct vhost_virtqueue *vq)
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{
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return vq_access_ok(vq->num, vq->desc, vq->avail, vq->used) &&
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vq_log_access_ok(vq, vq->log_base);
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return vq_access_ok(vq->dev, vq->num, vq->desc, vq->avail, vq->used) &&
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vq_log_access_ok(vq->dev, vq, vq->log_base);
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}
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static long vhost_set_memory(struct vhost_dev *d, struct vhost_memory __user *m)
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@ -577,6 +585,7 @@ static int init_used(struct vhost_virtqueue *vq,
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if (r)
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return r;
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vq->signalled_used_valid = false;
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return get_user(vq->last_used_idx, &used->idx);
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}
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@ -674,7 +683,7 @@ static long vhost_set_vring(struct vhost_dev *d, int ioctl, void __user *argp)
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* If it is not, we don't as size might not have been setup.
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* We will verify when backend is configured. */
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if (vq->private_data) {
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if (!vq_access_ok(vq->num,
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if (!vq_access_ok(d, vq->num,
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(void __user *)(unsigned long)a.desc_user_addr,
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(void __user *)(unsigned long)a.avail_user_addr,
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(void __user *)(unsigned long)a.used_user_addr)) {
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@ -818,7 +827,7 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, unsigned long arg)
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vq = d->vqs + i;
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mutex_lock(&vq->mutex);
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/* If ring is inactive, will check when it's enabled. */
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if (vq->private_data && !vq_log_access_ok(vq, base))
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if (vq->private_data && !vq_log_access_ok(d, vq, base))
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r = -EFAULT;
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else
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vq->log_base = base;
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@ -1219,6 +1228,10 @@ int vhost_get_vq_desc(struct vhost_dev *dev, struct vhost_virtqueue *vq,
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/* On success, increment avail index. */
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vq->last_avail_idx++;
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/* Assume notifications from guest are disabled at this point,
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* if they aren't we would need to update avail_event index. */
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BUG_ON(!(vq->used_flags & VRING_USED_F_NO_NOTIFY));
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return head;
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}
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@ -1267,6 +1280,12 @@ int vhost_add_used(struct vhost_virtqueue *vq, unsigned int head, int len)
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eventfd_signal(vq->log_ctx, 1);
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}
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vq->last_used_idx++;
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/* If the driver never bothers to signal in a very long while,
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* used index might wrap around. If that happens, invalidate
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* signalled_used index we stored. TODO: make sure driver
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* signals at least once in 2^16 and remove this. */
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if (unlikely(vq->last_used_idx == vq->signalled_used))
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vq->signalled_used_valid = false;
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return 0;
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}
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@ -1275,6 +1294,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
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unsigned count)
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{
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struct vring_used_elem __user *used;
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u16 old, new;
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int start;
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start = vq->last_used_idx % vq->num;
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@ -1292,7 +1312,14 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
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((void __user *)used - (void __user *)vq->used),
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count * sizeof *used);
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}
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vq->last_used_idx += count;
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old = vq->last_used_idx;
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new = (vq->last_used_idx += count);
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/* If the driver never bothers to signal in a very long while,
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* used index might wrap around. If that happens, invalidate
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* signalled_used index we stored. TODO: make sure driver
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* signals at least once in 2^16 and remove this. */
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if (unlikely((u16)(new - vq->signalled_used) < (u16)(new - old)))
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vq->signalled_used_valid = false;
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return 0;
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}
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@ -1331,29 +1358,47 @@ int vhost_add_used_n(struct vhost_virtqueue *vq, struct vring_used_elem *heads,
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return r;
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}
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/* This actually signals the guest, using eventfd. */
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void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
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static bool vhost_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
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{
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__u16 flags;
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__u16 old, new, event;
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bool v;
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/* Flush out used index updates. This is paired
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* with the barrier that the Guest executes when enabling
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* interrupts. */
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smp_mb();
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if (vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY) &&
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unlikely(vq->avail_idx == vq->last_avail_idx))
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return true;
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if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
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__u16 flags;
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if (__get_user(flags, &vq->avail->flags)) {
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vq_err(vq, "Failed to get flags");
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return;
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return true;
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}
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return !(flags & VRING_AVAIL_F_NO_INTERRUPT);
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}
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old = vq->signalled_used;
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v = vq->signalled_used_valid;
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new = vq->signalled_used = vq->last_used_idx;
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vq->signalled_used_valid = true;
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if (unlikely(!v))
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return true;
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if (get_user(event, vhost_used_event(vq))) {
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vq_err(vq, "Failed to get used event idx");
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return true;
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}
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return vring_need_event(event, new, old);
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}
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/* If they don't want an interrupt, don't signal, unless empty. */
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if ((flags & VRING_AVAIL_F_NO_INTERRUPT) &&
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(vq->avail_idx != vq->last_avail_idx ||
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!vhost_has_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY)))
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return;
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/* This actually signals the guest, using eventfd. */
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void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
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{
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/* Signal the Guest tell them we used something up. */
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if (vq->call_ctx)
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if (vq->call_ctx && vhost_notify(dev, vq))
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eventfd_signal(vq->call_ctx, 1);
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}
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@ -1376,7 +1421,7 @@ void vhost_add_used_and_signal_n(struct vhost_dev *dev,
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}
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/* OK, now we need to know about added descriptors. */
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bool vhost_enable_notify(struct vhost_virtqueue *vq)
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bool vhost_enable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
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{
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u16 avail_idx;
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int r;
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@ -1384,12 +1429,35 @@ bool vhost_enable_notify(struct vhost_virtqueue *vq)
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if (!(vq->used_flags & VRING_USED_F_NO_NOTIFY))
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return false;
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vq->used_flags &= ~VRING_USED_F_NO_NOTIFY;
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if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
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r = put_user(vq->used_flags, &vq->used->flags);
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if (r) {
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vq_err(vq, "Failed to enable notification at %p: %d\n",
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&vq->used->flags, r);
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return false;
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}
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} else {
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r = put_user(vq->avail_idx, vhost_avail_event(vq));
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if (r) {
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vq_err(vq, "Failed to update avail event index at %p: %d\n",
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vhost_avail_event(vq), r);
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return false;
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}
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}
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if (unlikely(vq->log_used)) {
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void __user *used;
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/* Make sure data is seen before log. */
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smp_wmb();
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used = vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX) ?
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&vq->used->flags : vhost_avail_event(vq);
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/* Log used flags or event index entry write. Both are 16 bit
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* fields. */
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log_write(vq->log_base, vq->log_addr +
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(used - (void __user *)vq->used),
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sizeof(u16));
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if (vq->log_ctx)
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eventfd_signal(vq->log_ctx, 1);
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}
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/* They could have slipped one in as we were doing that: make
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* sure it's written, then check again. */
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smp_mb();
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@ -1404,15 +1472,17 @@ bool vhost_enable_notify(struct vhost_virtqueue *vq)
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}
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/* We don't need to be notified again. */
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void vhost_disable_notify(struct vhost_virtqueue *vq)
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void vhost_disable_notify(struct vhost_dev *dev, struct vhost_virtqueue *vq)
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{
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int r;
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if (vq->used_flags & VRING_USED_F_NO_NOTIFY)
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return;
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vq->used_flags |= VRING_USED_F_NO_NOTIFY;
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if (!vhost_has_feature(dev, VIRTIO_RING_F_EVENT_IDX)) {
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r = put_user(vq->used_flags, &vq->used->flags);
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if (r)
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vq_err(vq, "Failed to enable notification at %p: %d\n",
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&vq->used->flags, r);
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}
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}
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@ -84,6 +84,12 @@ struct vhost_virtqueue {
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/* Used flags */
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u16 used_flags;
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/* Last used index value we have signalled on */
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u16 signalled_used;
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/* Last used index value we have signalled on */
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bool signalled_used_valid;
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/* Log writes to used structure. */
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bool log_used;
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u64 log_addr;
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@ -149,8 +155,8 @@ void vhost_add_used_and_signal(struct vhost_dev *, struct vhost_virtqueue *,
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void vhost_add_used_and_signal_n(struct vhost_dev *, struct vhost_virtqueue *,
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struct vring_used_elem *heads, unsigned count);
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void vhost_signal(struct vhost_dev *, struct vhost_virtqueue *);
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void vhost_disable_notify(struct vhost_virtqueue *);
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bool vhost_enable_notify(struct vhost_virtqueue *);
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void vhost_disable_notify(struct vhost_dev *, struct vhost_virtqueue *);
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bool vhost_enable_notify(struct vhost_dev *, struct vhost_virtqueue *);
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int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
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unsigned int log_num, u64 len);
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@ -162,11 +168,12 @@ int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
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} while (0)
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enum {
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VHOST_FEATURES = (1 << VIRTIO_F_NOTIFY_ON_EMPTY) |
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(1 << VIRTIO_RING_F_INDIRECT_DESC) |
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(1 << VHOST_F_LOG_ALL) |
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(1 << VHOST_NET_F_VIRTIO_NET_HDR) |
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(1 << VIRTIO_NET_F_MRG_RXBUF),
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VHOST_FEATURES = (1ULL << VIRTIO_F_NOTIFY_ON_EMPTY) |
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(1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
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(1ULL << VIRTIO_RING_F_EVENT_IDX) |
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(1ULL << VHOST_F_LOG_ALL) |
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(1ULL << VHOST_NET_F_VIRTIO_NET_HDR) |
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(1ULL << VIRTIO_NET_F_MRG_RXBUF),
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};
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static inline int vhost_has_feature(struct vhost_dev *dev, int bit)
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