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From: Huawei Xie <huawei.xie@intel.com>
To: dev@dpdk.org
Cc: mst@redhat.com
Subject: [dpdk-dev] [PATCH v2] vhost: flush used->idx update before reading avail->flags
Date: Wed, 29 Apr 2015 19:11:24 +0800	[thread overview]
Message-ID: <1430305884-9139-1-git-send-email-huawei.xie@intel.com> (raw)
In-Reply-To: <1429720392-25345-1-git-send-email-huawei.xie@intel.com>

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 <huawei.xie@intel.com>
---
 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

  parent reply	other threads:[~2015-04-29 11:11 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-22 16:33 [dpdk-dev] [PATCH] " Huawei Xie
2015-04-23 13:57 ` Luke Gorrie
2015-04-24  1:01 ` Linhaifeng
2015-04-24  2:40   ` Xie, Huawei
2015-04-24  7:27   ` Luke Gorrie
2015-06-09  7:04     ` Linhaifeng
2015-06-09  7:45       ` Luke Gorrie
2015-06-09  8:46       ` Michael S. Tsirkin
2015-06-09 13:34         ` Xie, Huawei
2015-06-10  2:36           ` Linhaifeng
2015-06-10  8:30         ` Luke Gorrie
2015-06-11  0:50           ` Linhaifeng
2015-04-29 11:11 ` Huawei Xie [this message]
2015-05-13 10:46   ` [dpdk-dev] [PATCH v2] " Thomas Monjalon
2015-05-15 13:43     ` Nikita Kalyazin
2015-05-15 15:23       ` Michael S. Tsirkin
2015-05-18  6:18         ` Nikita Kalyazin

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