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From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] Re: [PATCHv2 10/12] tap: add vhost/vhostfd options
Date: Tue, 2 Mar 2010 22:41:27 +0000
References: <cover.1267122331.git.mst@redhat.com>
	<20100302161247.GA25371@amt.cnet> <4B8D4350.6040506@codemonkey.ws>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: quintela@redhat.com, Marcelo Tosatti <mtosatti@redhat.com>, qemu-devel@nongnu.org, "Michael S. Tsirkin" <mst@redhat.com>, kraxel@redhat.com, amit.shah@redhat.com

> The new function I'm proposing has the following semantics:
> 
> - it always returns a persistent mapping
> - it never bounces
> - it will only fail if the mapping isn't ram

So you're assuming that virtio rings are in ram that is not hot-pluggable or 
remapable, and the whole region is contiguous?
That sounds like it's likely to come back and bite you. The guest has no idea 
which areas of ram happen to be contiguous on the host.

Paul