linux-kernel - RE: REGRESSION: 2.6.26-rc2-git4: X server failed start on X61s laptop

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Message-ID: <924EFEDD5F540B4284297C4DC59F3DEE01119AFE@orsmsx423.amr.corp.intel.com>
Date:	Sat, 17 May 2008 06:21:18 -0700
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	"Theodore Ts'o" <tytso@....edu>, <linux-kernel@...r.kernel.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Siddha, Suresh B" <suresh.b.siddha@...el.com>
Subject: RE: REGRESSION: 2.6.26-rc2-git4: X server failed start on X61s laptop

 

>-----Original Message-----
>From: Theodore Ts'o [mailto:tytso@....edu] 
>Sent: Saturday, May 17, 2008 12:32 AM
>To: linux-kernel@...r.kernel.org
>Cc: Pallipadi, Venkatesh
>Subject: REGRESSION: 2.6.26-rc2-git4: X server failed start on 
>X61s laptop
>
>
>The X server failed to come up using the Intel driver, and forced a
>fallback to the 800x600 VESA server.  This was on my Lenovo X61s laptop
>with an Intel chipset, running Ubuntu Gutsy.  When it failed, 
>there were
>a large number of these errors in the /var/log/messages:
>
>mtrr: type mismatch for e0760000,10000 old: write-back new: 
>write-combining
>mtrr: type mismatch for e0740000,20000 old: write-back new: 
>write-combining
>mtrr: type mismatch for e0700000,40000 old: write-back new: 
>write-combining
>mtrr: type mismatch for e0600000,100000 old: write-back new: 
>write-combining
>mtrr: type mismatch for e0400000,200000 old: write-back new: 
>write-combining
>mtrr: type mismatch for e0000000,400000 old: write-back new: 
>write-combining
>      ...
>
>On kernels where this error did not occur during the bisect, 
>there would
>still be one of these messages:
>
>mtrr: type mismatch for e0000000,10000000 old: write-back new: 
>write-combining
>
>... but the X server would correctly start.
>
>The git bisect identified this commit as the guilty one:
>
>1c12c4cf9411eb130b245fa8d0fbbaf989477c7b is first bad commit
>commit 1c12c4cf9411eb130b245fa8d0fbbaf989477c7b
>Author: Venki Pallipadi <venkatesh.pallipadi@...el.com>
>Date:   Wed May 14 16:05:51 2008 -0700
>
>    mprotect: prevent alteration of the PAT bits
>    
>    There is a defect in mprotect, which lets the user change 
>the page cache
>    type bits by-passing the kernel reserve_memtype and free_memtype
>    wrappers.  Fix the problem by not letting mprotect change 
>the PAT bits.
>    


Can you please send the complete dmesg after X failure, with patch here
and debugpat boot option.
http://www.ussg.iu.edu/hypermail/linux/kernel/0805.0/2657.html

Thanks,
Venki
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