[Xen-devel] [Fwd: Re: Wondering about cirris and stdvga]

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

-------- Forwarded Message --------
From: Adam Jackson <ajax@xxxxxxxxxx>
Subject: Re: Wondering about cirris and stdvga
Date: Fri, 18 Nov 2016 15:23:59 -0500
Message-Id: <1479500639.16973.3.camel@xxxxxxxxxx>

On Fri, 2016-11-18 at 11:26 -0800, Stefano Stabellini wrote:

> 
> I am no Xorg maintainer but back in the XenClient days we did some
> perf
> analysis and it turned out that the bitblt operations supported by
> Cirrus are actually very slow to emulate in QEMU.

Yep. Turns out the "acceleration" is still going to be running on a
CPU, so you can either take a hypercall for every operation, or not.

The X drivers for a while now have detected virtual cirrus devices and
defaulted to a shadow framebuffer instead, partly for this reason and
partly to hide the absolutely terrible 24bpp framebuffer format from
applications.

- ajax
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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