From c1a88ad1f4ac994cd70695bf08141d161e21533e Mon Sep 17 00:00:00 2001 From: Alex Bligh Date: Fri, 5 Apr 2013 15:45:15 +0000 Subject: [PATCH] Xen PV backend: Disable use of O_DIRECT by default as it results in crashes. Due to what is almost certainly a kernel bug, writes with O_DIRECT may continue to reference the page after the write has been marked as completed, particularly in the case of TCP retransmit. In other scenarios, this "merely" risks data corruption on the write, but with Xen pages from domU are only transiently mapped into dom0's memory, resulting in kernel panics when they are subsequently accessed. This brings PV devices in line with emulated devices. Removing O_DIRECT is safe as barrier operations are now correctly passed through. See: http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html for more details. Signed-off-by: Alex Bligh Signed-off-by: Stefano Stabellini --- hw/xen_disk.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/hw/xen_disk.c b/hw/xen_disk.c index 24e8b2491a..1a30f0a9ed 100644 --- a/hw/xen_disk.c +++ b/hw/xen_disk.c @@ -782,7 +782,7 @@ static int blk_connect(struct XenDevice *xendev) int pers, index, qflags; /* read-only ? */ - qflags = BDRV_O_NOCACHE | BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO; + qflags = BDRV_O_CACHE_WB | BDRV_O_NATIVE_AIO; if (strcmp(blkdev->mode, "w") == 0) { qflags |= BDRV_O_RDWR; }