[dpdk-stable] patch 'vhost: make page logging atomic' has been queued to LTS release 16.11.3

[Yuanhan Liu]

Hi,

FYI, your patch has been queued to LTS release 16.11.3

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/11/17. So please
shout if anyone has objections.

Thanks.

	--yliu

---
>From c2d9c76b26d6626979ada03206a268b55d8f1248 Mon Sep 17 00:00:00 2001
From: Tiwei Bie <tiwei.bie at intel.com>
Date: Tue, 1 Aug 2017 17:01:21 +0800
Subject: [PATCH] vhost: make page logging atomic

[ backported from upstream commit 897f13a1f726cefdc68762da83f9d2225a85c27e ]

Each dirty page logging operation should be atomic. But it's not
atomic in current implementation. So it's possible that some dirty
pages can't be logged successfully when different threads try to
log different pages into the same byte of the log buffer concurrently.
This patch fixes this issue.

Fixes: b171fad1ffa5 ("vhost: log used vring changes")

Reported-by: Xiao Wang <xiao.w.wang at intel.com>
Signed-off-by: Tiwei Bie <tiwei.bie at intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin at redhat.com>
---
 lib/librte_vhost/virtio_net.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index ec9f1e5..0027f39 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -50,10 +50,19 @@
 #define MAX_PKT_BURST 32
 #define VHOST_LOG_PAGE	4096
 
+/*
+ * Atomically set a bit in memory.
+ */
+static inline void __attribute__((always_inline))
+vhost_set_bit(unsigned int nr, volatile uint8_t *addr)
+{
+	__sync_fetch_and_or_8(addr, (1U << nr));
+}
+
 static inline void __attribute__((always_inline))
 vhost_log_page(uint8_t *log_base, uint64_t page)
 {
-	log_base[page / 8] |= 1 << (page % 8);
+	vhost_set_bit(page % 8, &log_base[page / 8]);
 }
 
 static inline void __attribute__((always_inline))
-- 
2.7.4