From 159793ac867be6020309f2909f8c47afbf52ed3f Mon Sep 17 00:00:00 2001 From: Huawei Xie Date: Wed, 29 Apr 2015 19:11:24 +0800 Subject: [PATCH] vhost: fix virtio freeze due to missed interrupt Update of used->idx and read of avail->flags could be reordered. Memory fence should be used to ensure the order, otherwise guest could see a stale used->idx value after it toggles the interrupt suppression flag. After guest sets the interrupt suppression flag, it will check if there is more buffer to process through used->idx. If it sees a stale value, it will exit the processing while host won't send interrupt to guest. Signed-off-by: Huawei Xie Reviewed-by: Luke Gorrie --- lib/librte_vhost/vhost_rxtx.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c index 510ffe82ab..4809d32709 100644 --- a/lib/librte_vhost/vhost_rxtx.c +++ b/lib/librte_vhost/vhost_rxtx.c @@ -178,6 +178,9 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id, *(volatile uint16_t *)&vq->used->idx += count; vq->last_used_idx = res_end_idx; + /* flush used->idx update before we read avail->flags. */ + rte_mb(); + /* Kick the guest if necessary. */ if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) eventfd_write((int)vq->callfd, 1); @@ -505,6 +508,9 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id, *(volatile uint16_t *)&vq->used->idx += entry_success; vq->last_used_idx = res_end_idx; + /* flush used->idx update before we read avail->flags. */ + rte_mb(); + /* Kick the guest if necessary. */ if (!(vq->avail->flags & VRING_AVAIL_F_NO_INTERRUPT)) eventfd_write((int)vq->callfd, 1); -- 2.20.1