Re: i915 KMS framebuffer issues in 4.2.1/3.7.1.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Wed, Dec 26, 2012 at 08:39:24AM -0600, Dr. Greg Wettstein wrote:
> Good morning, hope the week is going well for everyone.
> 
> We have been putting 4.2.1 through its paces and noted an issue which
> is specific to the kernel running on top of the hypervisor.  It isn't
> specific to 4.2.1 but we validated the issue on this platform and on
> the 3.7.1 kernel for completeness.
> 
> An attempt to mmap the framebuffer provided by the i915 KMS driver
> causes a fork() to fail with ENOMEM.  Same hardware and kernel on

Is the kernel compiled with CONFIG_INTEL_DMAR .. something?

> bare-metal works fine.  The 'fbterm' utility demonstrates the problem
> but we can demonstrate on a minimal implemenation of 'mmap + forkpty'.

It could be that the _PAGE_IOMAP flag needs to be set. There was a patch
floating around for that. Hmm, could be this:

http://git.kernel.org/?p=linux/kernel/git/konrad/xen.git;a=commit;h=0cfd8ac8e702db147a9a664212f597f627b3f7e9

or these two patches:
http://git.kernel.org/?p=linux/kernel/git/konrad/xen.git;a=shortlog;h=refs/heads/devel/ioperm

but not sure.
> 
> Would be happy to test any patches or ideas if people have a though on
> the issue.
> 
> Have a good day.
> 
> As always,
> Dr. G.W. Wettstein, Ph.D.   Enjellic Systems Development, LLC.
> 4206 N. 19th Ave.           Specializing in information infra-structure
> Fargo, ND  58102            development.
> PH: 701-281-1686
> FAX: 701-281-3949           EMAIL: greg@enjellic.com
> ------------------------------------------------------------------------------
> "Experience is something you don't get until just after you need it."
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> 
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