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

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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 (2.6.31.4 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).
    J

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