On Wed, Aug 20, 2008 at 6:20 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
quoted text
> On Wed, Aug 20, 2008 at 6:04 PM, Andrew Morton
> <akpm@linux-foundation.org> wrote:
>>
>> (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.
> reg00: base=0xd0000000 (3328MB), size=196864MB: uncachable, count=1
> reg01: base=0xe0000000 (3584MB), size=197120MB: uncachable, count=1
> reg02: base=0x00000000 (   0MB), size=212992MB: write-back, count=1
> reg03: base=0x400000000 (16384MB), size=197120MB: write-back, count=1
> reg04: base=0x420000000 (16896MB), size=196864MB: write-back, count=1
>
> the size mtrr looks crazy.

please apply attached patch and boot with show_msr=1 to dump the msr
(including mtrr)

YH