From mboxrd@z Thu Jan 1 00:00:00 1970 From: Huawei Xie Subject: [PATCH v2] vhost: flush used->idx update before reading avail->flags Date: Wed, 29 Apr 2015 19:11:24 +0800 Message-ID: <1430305884-9139-1-git-send-email-huawei.xie@intel.com> References: <1429720392-25345-1-git-send-email-huawei.xie@intel.com> Cc: mst-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org To: dev-VfR2kkLFssw@public.gmane.org Return-path: In-Reply-To: <1429720392-25345-1-git-send-email-huawei.xie-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" 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 willn't send interrupt to guest. Signed-off-by: Huawei Xie --- 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 510ffe8..4809d32 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); -- 1.8.1.4