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Date: Sun, 28 Feb 2010 16:44:13 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] Re: [PATCHv2 09/12] vhost: vhost net support
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To: Paul Brook <paul@codesourcery.com>
Cc: amit.shah@redhat.com, quintela@redhat.com, qemu-devel@nongnu.org, kraxel@redhat.com

On Sun, Feb 28, 2010 at 12:45:07PM +0000, Paul Brook wrote:
> > >  There certainly
> > > exist machines that can change physical RAM mapping.
> > 
> > I am talking about mapping between phy RAM offset and qemu virt address.
> > When can it change without RAM in question going away?
> 
> RAM offset or guest physical address? The two are very different.

RAM offset. virtio only cares about where the rings are.

> Some machines have chip selects that allow given physical address range to be 
> mapped to different banks of ram.
> 
> Paul

So guest can cause vhost to write to a wrong place in RAM, but it can
just pass a wrong address directly.  As long as vhost does not access a
non-RAM address, we are definitely fine.

-- 
MST