Re: [Xen-devel] Frame buffer mmap not working in pvops dom0

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Jul 21, 2010 at 05:16:13PM +0300, Pasi Kärkkäinen wrote:
> On Wed, Jul 21, 2010 at 09:47:57AM -0400, Daniel De Graaf wrote:
> > I'm trying to confirm the fix to the VESA fbdev mmap issue that was
> > brought up a few months ago
> > (http://marc.info/?l=xen-devel&m=126842551306571&w=2). The wiki page at

Weird. I don't remember seeing that e-mail..

> > http://wiki.xensource.com/xenwiki/XenPVOPSDRM says that this bug should
> > be fixed, but doesn't point to a patch for the fix. I am still able to
> > reproduce the issue both on real hardware and by running Xen under qemu
> > (using cirrusfb on the dom0). Eamon (the original reporter) has also not
> > been able to confirm a fix.
> > 
> > I'm currently testing using Xen 4.1 built from hg 21831:6bebaf40e925 and
> > a pvops dom0 from xen/stable-2.6.32.x revid c0a00fbe.
> > 
> > So far, I've been able to determine that an mmap requesting multiple
> > pages from /dev/fb0 will result in page table entries all pointing to
> > the same physical page, which is not in the framebuffer address space.
> > Writing to the mapped page ends up corrupting parts of kernel memory.
> > I'd be happy to run further tests, try patches, or provide more
> > information if needed.

Goodies. Let me fix up a tree that cleanly merges with Jeremy's xen/next
(or xen/stable-2.6.32.x) and give you a go with that. And then from
there we can come up with a fix.

Can you tell me how you came up with the analysis? (that should speed up
finding the culprit). Any serial/dmesg outputs would be appreciated.

> > 
> 
> I guess many (most?) graphics related fixes are in Konrad's git tree..

<nods>

Daniel,

I honestly don't remember which patch I thought fixed it. But I do know
that when the /dev/fb0 was backed by DRM (nvidia) it worked (I used the 
below program).

Granted now that I tested it with fbxine and it hangs with a Xen error.
Let me start using Eamon's program.

Attachment: fb_test.c
Description: Text document

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