Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of 16gb of memory is usable

Andrew Morton
2008-08-21T01:04:36Z

(switched to email. Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Wed, 20 Aug 2008 17:38:59 -0700 (PDT)
bugme-daemon@bugzilla.kernel.org wrote:

> http://bugzilla.kernel.org/show_bug.cgi?id=11388
>
> Summary: 2.6.27-rc3 warns about MTRR range; only 3 of 16gb of
> memory is usable
> Product: Memory Management
> Version: 2.5
> KernelVersion: 2.6.27-rc3
> Platform: All
> OS/Version: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: MTTR
> AssignedTo: akpm@osdl.org
> ReportedBy: j_kernel@hoblitt.com
>
>
> Latest working kernel version: 2.4.24.2 (possibly later)
> Earliest failing kernel version: 2.6.27-rc3-21328-ga7f5aaf (from netdev-2.6)
> Distribution: Gentoo
> Hardware Environment: 2x Intel X5482
> Software Environment:
> Problem Description:
>
> [ 0.000000] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing
> 13056MB of RAM.
> [ 0.000000] ------------[ cut here ]------------
> [ 0.000000] WARNING: at arch/x86/kernel/cpu/mtrr/main.c:1561
> mtrr_trim_uncached_memory+0x508/0x550()
> [ 0.000000] Modules linked in:
> [ 0.000000] Pid: 0, comm: swapper Not tainted 2.6.27-rc3-21328-ga7f5aaf #8
> [ 0.000000]
> [ 0.000000] Call Trace:
> [ 0.000000] [<ffffffff80234c3e>] warn_on_slowpath+0x51/0x77
> [ 0.000000] [<ffffffff8023570a>] printk+0x4e/0x56
> [ 0.000000] [<ffffffff803add02>] sort+0xfa/0x18c
> [ 0.000000] [<ffffffff808283d3>] cmp_range+0x0/0x6
> [ 0.000000] [<ffffffff80828a47>] mtrr_trim_uncached_memory+0x508/0x550
> [ 0.000000] [<ffffffff802178e1>] post_set+0x20/0x3d
> [ 0.000000] [<ffffffff80824f99>] setup_arch+0x39d/0x6be
> [ 0.000000] [<ffffffff8081e962>] start_kernel+0x74/0x341
> [ 0.000000] [<ffffffff8081e394>] x86_64_start_kernel+0xe3/0xe7
> [ 0.000000]
> [ 0.000000] ---[ end trace 4eaa2a86a8e2da22 ]---
>
>
> Steps to reproduce:
>
> This warning isn't present under 2.6.24.2 and the full range of physical memory
> is usable.

Looks like a post-2.6.26 regression caused by
12031a624af7816ec7660b82be648aa3703b4ebe.