Out of MTRRs at boot

Question

It seems my laptop (an Acer Aspire One AOA150) runs out of MTRRs at boot. I've done some googling on the problem and read that people recommend turning on MTRR sanitizing to fix it, however, it still occurs. This occurs both with -ARCH and my own kernel config.
You can see that I have enabled MTRR sanitization here:
[chris@helios ~]$ zcat /proc/config.gz | fgrep 'SANITIZER'
CONFIG_MTRR_SANITIZER=y
CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT=1
CONFIG_MTRR_SANITIZER_SPARE_REG_NR_DEFAULT=1
Here is my system info (more than you'll need, just my standard printout):
http://pastie.org/private/eqatevtzhhwfwwxrzkxq
Thanks in advance for any help
Last edited by neurolysis (2011-04-01 13:43:33)

Answer 1

fphillips wrote:
From the dmesg, it is easy to see that it runs out of mtrr during i915/drm graphics initialization. I have no specific experience with this problem, but here's my suggestions:
1. Boot with mtrr_spare_reg_nr=2 and you may also need enable_mtrr_cleanup=1 (add to kernel line in /boot/grub/menu.lst).
2. Try kernel 2.6.38 from [testing].
http://www.mjmwired.net/kernel/Document … s.txt#1529
http://fixunix.com/kernel/388642-patch- … out-4.html
No luck with either (I already had enable_mtrr_cleanup=1, which just changes CONFIG_MTRR_SANITIZER_ENABLE_DEFAULT, but booting with  mtrr_spare_reg_nr=2 doesn't fix it either). The error from drm has now disappeared, but this still remains:
[ 0.329894] mtrr: no more MTRRs available
Gusar wrote:But the thing is, mtrr is not relevant for graphics, because they use pat anyway. That line is only relevant for machines without pat (or if you boot with nopat on the kernel commandline).
Is there a good way to test this? Does the pat flag in /proc/cpuinfo indicate that MTRRs will not be used?
Last edited by neurolysis (2011-04-04 19:25:07)