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Date: Thu, 31 Mar 2011 13:33:58 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [PATCH RFC] vga: flag vga ram for notifiers
References: <20110331174328.GA25133@redhat.com>
In-Reply-To: <20110331174328.GA25133@redhat.com>
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: qemu-devel@nongnu.org

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

There is nothing special about VGA.

Regards,

Anthony Liguori