bugGNU GRUB - Bugs: bug #38597, MTRR inconsistency between BSP and...

 
 

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bug #38597: MTRR inconsistency between BSP and APs

Submitted by:  Helge Wagner <helge>
Submitted on:  Tue 26 Mar 2013 01:02:26 PM UTC  
 
Category: BootingSeverity: Major
Priority: 5 - NormalItem Group: Software Error
Status: NonePrivacy: Public
Assigned to: NoneOriginator Name: 
Open/Closed: OpenRelease: 
Release: otherReproducibility: Every Time
Planned Release: None

Fri 12 Apr 2013 07:31:56 AM UTC, comment #2:

I will try it.
Can you give me some hints how to build/install the latest revision on debian or ubuntu?
Is there an easy way to write some debug messages to a serial console?

Helge Wagner <helge>
Mon 01 Apr 2013 12:23:44 AM UTC, comment #1:

GRUB is meant to disable this mtrr entry before handing over to kernel (in get_info_and_fini / vbe_fini). Can you look why this doesn't happen?

Vladimir Serbinenko <phcoder>
Project Administrator
Tue 26 Mar 2013 01:02:26 PM UTC, original submission:

As a BIOS/UEFI Firmware engineer I was looking through the boot log of an OpenSuSE 12.3 system to search for error messages which might indicate failures in our UEFI Firmware.
On our VIA based system I found this one:
"mtrr: your CPUs had inconsistent variable MTRR settings"

Further researching I found that this is caused by grub2 (the grub2 used by OpenSuSE12.3; I am not sure which release that is): If I boot-up my OpenSuSE through PXELINUX (just loaded kernel and initrd through tftp, the rest of the system still on local hard disk), then the error message is gone.
Looking into the source code of grub2 I found the root cause of the problem:

"grub-core/video/i386/pc/vbe.c" has a function "grub_vbe_enable_mtrr()" which sets a WC MTRR if the framebuffer is not already covered by a MTRR.
It does this on BSP CPU only. So after this code is run, the MTRRs between BSP and APs are inconsistent.

Helge Wagner <helge>

 

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