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Date: Thu, 31 Mar 2011 20:49:41 +0200
From: "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [Qemu-devel] [PATCH RFC] vga: flag vga ram for notifiers
Message-ID: <20110331184940.GA25688@redhat.com>
References: <20110331174328.GA25133@redhat.com>
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: qemu-devel@nongnu.org

On Thu, Mar 31, 2011 at 01:33:58PM -0500, Anthony Liguori wrote:
> On 03/31/2011 12:43 PM, Michael S. Tsirkin wrote:
> >Currently, vga cards that allocate vga ram,
> >register it as regular ram. When this happens
> >a lot, vhost need to get notified and flush
> >its memory tables, which is slow.
> >
> >This was observed with cirrus vga.
> >
> >As a solution, add an explicit flag when
> >registering vga ram, vhost-net can simply ignore it.
> >
> >Long term, we might be able to use this API
> >to avoid the need to request
> >dirty loggin from devices explicitly.
> >
> >Tested: with cirrus vga only.
> >
> >Signed-off-by: Michael S. Tsirkin<mst@redhat.com>
> 
> Treating vga specially is not the right approach.
> 
> You want to treat real RAM specially and only make that visible to
> vhost.  See http://wiki.qemu.org/Features/RamAPI

That seems like a dead project? And VGa is unhandled there.


> There is nothing special about VGA.

It is special in that guest can control host virtual to
guest physical mappings. In this VGA is similar to 
IO rather than RAM.


-- 
MST