linux-kernel - RE: [Bug 10843] Display artifacts on XOrg logout with PAT kernel and VESA framebuffer

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Message-ID: <8B23168BCBB43B49A4C8EAB32D4B62F1061F3A82@orsmsx505.amr.corp.intel.com>
Date:	Sun, 15 Jun 2008 12:29:24 -0700
From:	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
To:	Frans Pop <elendil@...net.nl>, "Rafael J. Wysocki" <rjw@...k.pl>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	"arjan@...ux.intel.com" <arjan@...ux.intel.com>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>
Subject: RE: [Bug 10843] Display artifacts on XOrg logout with PAT kernel
 and VESA framebuffer

Frans Pop wrote:
> On Saturday 14 June 2008, Rafael J. Wysocki wrote:
> > The following bug entry is on the current list of known regressions
> > from 2.6.25.  Please verify if it still should be listed.
> >
> > Bug-Entry     : http://bugzilla.kernel.org/show_bug.cgi?id=10843
> > Subject       : Display artifacts on XOrg logout with PAT kernel and VESA
> >                 framebuffer
> > Submitter     : Frans Pop <elendil@...net.nl>
> > Date          : 2008-05-31 14:04 (15 days old)
> > References    : http://lkml.org/lkml/2008/6/7/206
>
> Yes. See also: http://lkml.org/lkml/2008/6/13/159

Frans, With or with out pat, in the recent kernels (like 2.6.26-rc4/rc5 etc), ioremap()
uses  UC- and PCI mmap of /sys/devices/pci.../resource (used by X) uses UC-

And fb_mmap() also uses UC-.

It's interesting that you don't see this artifact with "nopat". Essentially with
or with out pat enabled, we use the same memory attributes. So depending on the
MTRR setup (set by X server), effective memory attribute across different mappings
should be same (which is UC- or WC with mtrr).

Can you also check, if there is any impact with kernel boot param for vesafb "mtrr:3"?

thanks,
suresh
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