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Date: Mon, 21 May 2012 10:11:06 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] Add a memory barrier to guest memory
	access functions
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To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: David Gibson <david@gibson.dropbear.id.au>, qemu-devel@nongnu.org, Anthony Liguori <anthony@codemonkey.ws>, "Michael S. Tsirkin" <mst@redhat.com>

Il 21/05/2012 03:56, Benjamin Herrenschmidt ha scritto:
> I don't see an obvious need to provide a "relaxed" variant of the
> later at this stage, a quick grep doesn't seem to show that most cases
> where it's used are either not performance sensitive or the barrier
> makes sense, but feel free to prove me wrong :-)

The only problem here is that you have useless memory barriers when
calling cpu_physical_memory_map in a loop (see virtqueue_map_sg).

Paolo