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Date: Thu, 31 Mar 2011 23:38:49 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH RFC] vga: flag vga ram for notifiers
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: Alex Williamson <alex.williamson@redhat.com>, qemu-devel@nongnu.org

On Thu, Mar 31, 2011 at 10:32:11PM +0100, Peter Maydell wrote:
> On 31 March 2011 21:23, Anthony Liguori <anthony@codemonkey.ws> wrote:
> > On 03/31/2011 03:12 PM, Peter Maydell wrote:
> >> Well, obviously you need to be able to revoke the permission
> >> to use the fastpath pointer to the underlying memory. But you
> >> need to be able to do that anyhow, to cover cases where (eg) the
> >> guest has just written to some register that remaps the bottom
> >> part of the address space so it's ROM rather than RAM, or whatever.
> >> It's just a feature your optimisation needs to have. Equally, you
> >> don't remap unless you have to, but if the mapping's changed then
> >> it's changed...
> >
> > Right, the trouble now is that there's no way to distinguish between mapping
> > where 1) we don't care about them in virtio and 2) they change frequently.
> 
> Aha. Thanks for the explanation.
> 
> > Maybe the right approach here is to just use a virtio specific API and
> > register RAM as register_virtio_dma_area().
> 
> That seems like a clearer API, yes. I think it makes it much more
> obvious what it's trying to achieve.
> 
> -- PMM

Maybe register_dma_area - its' not 100% virtio specific.

-- 
MST