From: Jason Wang <jasowang@redhat.com>
To: rusty@rustcorp.com.au, mst@redhat.com,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Cc: davem@davemloft.net, eric.dumazet@gmail.com,
Jason Wang <jasowang@redhat.com>
Subject: [RFC PATCH net-next 1/6] virtio: make sure used event never go backwards
Date: Wed, 15 Oct 2014 15:25:25 +0800 [thread overview]
Message-ID: <1413357930-45302-2-git-send-email-jasowang@redhat.com> (raw)
In-Reply-To: <1413357930-45302-1-git-send-email-jasowang@redhat.com>
This patch checks the new event idx to make sure used event idx never
goes back. This is used to synchronize the calls between
virtqueue_enable_cb_delayed() and virtqueue_enable_cb().
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/virtio/virtio_ring.c | 7 +++++--
1 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 3b1f89b..1b3929f 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -559,14 +559,17 @@ unsigned virtqueue_enable_cb_prepare(struct virtqueue *_vq)
u16 last_used_idx;
START_USE(vq);
-
+ last_used_idx = vq->last_used_idx;
/* We optimistically turn back on interrupts, then check if there was
* more to do. */
/* Depending on the VIRTIO_RING_F_EVENT_IDX feature, we need to
* either clear the flags bit or point the event index at the next
* entry. Always do both to keep code simple. */
vq->vring.avail->flags &= ~VRING_AVAIL_F_NO_INTERRUPT;
- vring_used_event(&vq->vring) = last_used_idx = vq->last_used_idx;
+ /* Make sure used event never go backwards */
+ if (!vring_need_event(vring_used_event(&vq->vring),
+ vq->vring.avail->idx, last_used_idx))
+ vring_used_event(&vq->vring) = last_used_idx;
END_USE(vq);
return last_used_idx;
}
--
1.7.1
next prev parent reply other threads:[~2014-10-15 7:44 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-15 7:25 [RFC PATCH net-next 0/6] Always use tx interrupt for virtio-net Jason Wang
2014-10-15 7:25 ` Jason Wang [this message]
2014-10-15 9:34 ` [RFC PATCH net-next 1/6] virtio: make sure used event never go backwards Michael S. Tsirkin
2014-10-15 10:13 ` Jason Wang
2014-10-15 10:32 ` Michael S. Tsirkin
2014-10-15 10:44 ` Jason Wang
2014-10-15 11:38 ` Michael S. Tsirkin
2014-10-17 5:04 ` Jason Wang
2014-10-15 7:25 ` [RFC PATCH net-next 2/6] virtio: introduce virtio_enable_cb_avail() Jason Wang
2014-10-15 9:28 ` Michael S. Tsirkin
2014-10-15 10:19 ` Jason Wang
2014-10-15 10:41 ` Michael S. Tsirkin
2014-10-15 10:58 ` Jason Wang
2014-10-15 11:43 ` Michael S. Tsirkin
2014-10-15 7:25 ` [RFC PATCH net-next 3/6] virtio-net: small optimization on free_old_xmit_skbs() Jason Wang
2014-10-15 9:36 ` Eric Dumazet
2014-10-15 9:37 ` Michael S. Tsirkin
2014-10-15 9:49 ` David Laight
2014-10-15 10:48 ` Michael S. Tsirkin
2014-10-15 10:51 ` David Laight
2014-10-15 12:00 ` Michael S. Tsirkin
2014-10-15 7:25 ` [RFC PATCH net-next 4/6] virtio-net: return the number of packets sent in free_old_xmit_skbs() Jason Wang
2014-10-15 7:25 ` [RFC PATCH net-next 5/6] virtio-net: enable tx interrupt Jason Wang
2014-10-15 9:37 ` Eric Dumazet
2014-10-15 10:21 ` Jason Wang
2014-10-15 10:18 ` Michael S. Tsirkin
2014-10-15 10:25 ` Jason Wang
2014-10-15 10:43 ` Michael S. Tsirkin
2014-10-15 11:00 ` Jason Wang
2014-10-15 7:25 ` [RFC PATCH net-next 6/6] virtio-net: enable tx interrupt only for the final skb in the chain Jason Wang
2014-10-15 10:22 ` Michael S. Tsirkin
2014-10-15 10:31 ` Jason Wang
2014-10-15 10:46 ` Michael S. Tsirkin
2014-10-15 10:25 ` [RFC PATCH net-next 0/6] Always use tx interrupt for virtio-net Michael S. Tsirkin
2014-10-15 11:14 ` Jason Wang
2014-10-15 11:58 ` Michael S. Tsirkin
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