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Re: [Xen-devel] Fbdev graphics broken in xen/next dom0

To: Eamon Walsh <ewalsh@xxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Fbdev graphics broken in xen/next dom0
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Fri, 12 Mar 2010 16:51:30 -0800
Cc: George Coker <gscoker@xxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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On 03/12/2010 04:44 PM, Eamon Walsh wrote:
I have narrowed the problem down: it has something to do with mmap of
/dev/fb0 not syncing.  The attached C code mmaps /dev/fb0 and writes
some random bits.  On a configuration that does work ( on
4.0-rc6, or xen/next on bare metal) the random bits are visible on the
screen.  With xen/next on 4.0-rc6, nothing is visible.  Calling msync()
before the sleep has no effect.  Also, using write() on /dev/fb0 always
works so it appears to be mmap related.

Yes. I suspect there's a missing VM_IO in there, and so the mmap is mapping the wrong pages (if you're lucky you might be able to crash the machine to see something juicy).


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