From: Brian Kress <kressb@moose.net>
To: Duck <duck@roaming.ath.cx>
Cc: kvm@vger.kernel.org
Subject: Re: kvm-84 -- Cirrus video updates bad on XP
Date: Sat, 21 Feb 2009 10:53:56 -0500 [thread overview]
Message-ID: <49A02394.4010702@moose.net> (raw)
In-Reply-To: <alpine.LNX.2.00.0902211612100.8317@duo>
Two seperate problems. The Cirrus VGA issue is due to it trying to
be clever about video to video copies, which is why you see it during
scrolling and window dragging. I posted patch that (sort of) fixes it,
but doesn't completely. This whole area of code is doing something
very iffy and getting it to do it correctly seems very hard.
The std vga issue is because when the framebuffer is 32 bits (std
vga is 32, cirrus vga is 24), the vga driver ends up sharing the vram
framebuffer with the display surface. This is interesting and means
less copying, however it doesn't seem to be safe, as you end up with the
display driver reading memory out of vram and the same time as the guest
is writing to it. Hence you end up with weirdness.
-Brian
Duck wrote:
> Patchy video updates also seems to happen, though less obviously, with
> '-vga std'.
>
> For example, I started an XP guest with 'vga std' and then forgot about it
> for some time. When I next looked at it, the screen saver had kicked in
> (the jumping "Windows" logo) but only the bottom half of the logo was
> visible as it bounced around.
>
> Host is Linux 2.6.27.7 with kvm drivers built from the kvm-84 source tree.
> Guest is XP0.
>
> Haven't seen this behaviour with kvm-83.
>
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next prev parent reply other threads:[~2009-02-21 16:14 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-21 5:19 kvm-84 -- Cirrus video updates bad on XP Duck
2009-02-21 15:53 ` Brian Kress [this message]
-- strict thread matches above, loose matches on Subject: below --
2009-02-21 2:52 Duck
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