Bug 14448

Summary:	PAT cpu feature is absent but detected by Xorg and others, cuses video driver problems
Product:	Memory Management	Reporter:	Aleksei Lukin (lukin)
Component:	MTTR	Assignee:	Andrew Morton (akpm)
Status:	CLOSED UNREPRODUCIBLE
Severity:	normal	CC:	florian, rjw
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.31-14-generic #48-Ubuntu SMP	Subsystem:
Regression:	Yes	Bisected commit-id:
Bug Depends on:
Bug Blocks:	13615
Attachments:	output of cat /proc/cpuinfo and x86info

Description Aleksei Lukin 2009-10-20 17:54:18 UTC

On Intel-M (Dothan) [B-1] PAT feature is absent and kernel says so in /proc/cpuinfo and in kernel messages in boot time. But certain programs like Xorg, x86info "see" PAT support and take wrong behavior path.

For instance, nouveau driver just hangs on latest Ubuntu 9.10, nvidia drivers can not load GL support and so on. 

Problem can be solved by passing "nopat" argument in kernel command line and then everithing works, but x86info still reports "pat" in CPU flags.

The same situation in latest Fedora 11 kernels. 

output of cat /proc/cpuinfo and x86info are attached.
Related Ubuntu bug discussion is here: 
https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-180/+bug/391461

Comment 1 Aleksei Lukin 2009-10-20 17:56:52 UTC

Created attachment 23479 [details]
output of cat /proc/cpuinfo and x86info

output of cat /proc/cpuinfo and x86info

Comment 2 Florian Mickler 2011-02-06 15:04:12 UTC

Hi Aleksei!
Did this get resolved somehow, or is this still an issue?

Comment 3 Aleksei Lukin 2011-02-07 09:40:21 UTC

Yes, it resolved since Fedora 12, can not remember which kernel version.

Comment 4 Florian Mickler 2011-03-05 00:16:08 UTC

Thanks for the update.