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Date: Wed, 11 Nov 2009 11:37:37 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Message-ID: <20091111093737.GA3276@redhat.com>
References: <20091026131715.GA25271@redhat.com>
	<200911110134.13064.paul@codesourcery.com>
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Subject: [Qemu-devel] Re: [PATCH] qemu/virtio: make wmb compiler barrier +
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To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org

On Wed, Nov 11, 2009 at 01:34:12AM +0000, Paul Brook wrote:
> On Monday 26 October 2009, Michael S. Tsirkin wrote:
> > wmb must be at least a compiler barrier, even without SMP.
> 
> Why?

Because virtio code might run on a separate thread from guest.
If compiler reorders writes, guest might see inconsistent data.

-- 
MST