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Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers

From: Michael S. Tsirkin
Subject: Re: [Qemu-devel] [PATCH] virtio: Make memory barriers be memory barriers
Date: Fri, 2 Sep 2011 18:57:48 +0300
User-agent: Mutt/1.5.21 (2010-09-15)

On Fri, Sep 02, 2011 at 08:11:29AM +0200, Paolo Bonzini wrote:
> On 09/02/2011 02:11 AM, David Gibson wrote:
> >>>>  >Why not limit the change to ppc then?
> >>>
> >>>  Because the bug is masked by the x86 memory model, but it is still
> >>>  there even there conceptually.  It is not really true that x86 does
> >>>  not need memory barriers, though it doesn't in this case:
> >>>
> >>>  
> >>> http://bartoszmilewski.wordpress.com/2008/11/05/who-ordered-memory-fences-on-an-x86/
> >Not to mention that pcc is not the only non-x86 architecture.  I don't
> >know all their storage models off hand, but the point is that there is
> >a required order to these writes, so there should be a memory barrier.
> Indeed, I interpreted Michael's question more as "why not limit the
> change to non-x86".  I think we should cater to all memory models
> except perhaps the Alpha's.
> Paolo

Yes, x86 is pretty popular.

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