[coreboot] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 2MB of RAM

Joseph Smith joe at settoplinux.org
Sat Jun 12 16:05:56 CEST 2010

While working on my i810 port I am getting this message from the Linux 
kernel about my mtrr setup:

BIOS-provided physical RAM map:
  BIOS-e820: 0000000000000000 - 0000000000001000 type 16
  BIOS-e820: 0000000000001000 - 00000000000a0000 (usable)
  BIOS-e820: 00000000000c0000 - 000000000fef0000 (usable)
  BIOS-e820: 000000000fef0000 - 000000000ff00000 type 16
DMI not present or invalid.
last_pfn = 0xfef0 max_arch_pfn = 0x100000
WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 2MB of RAM.
------------[ cut here ]------------
WARNING: at arch/x86/kernel/cpu/mtrr/main.c:1557 
mtrr_trim_uncached_memory+0x295/0x2b6() (Not tainted)
Modules linked in:
Pid: 0, comm: swapper Not tainted #1
  [<c042ddfb>] warn_on_slowpath+0x65/0x8b
  [<c06ab53c>] ? _spin_unlock_irqrestore+0x1b/0x38
  [<c06ab53c>] ? _spin_unlock_irqrestore+0x1b/0x38
  [<c06ab543>] ? _spin_unlock_irqrestore+0x22/0x38
  [<c042e2f1>] ? release_console_sem+0x1bf/0x1c7
  [<c042e76c>] ? vprintk+0x2ce/0x2f3
  [<c06a96db>] ? printk+0xf/0x14
  [<c0824127>] mtrr_trim_uncached_memory+0x295/0x2b6
  [<c081f73b>] setup_arch+0x48f/0x947
  [<c042e76c>] ? vprintk+0x2ce/0x2f3
  [<c08218dd>] ? __reserve_early+0xe4/0xf8
  [<c06a96db>] ? printk+0xf/0x14
  [<c0819605>] start_kernel+0x73/0x2f0
  [<c0819080>] __init_begin+0x80/0x88
---[ end trace 4eaa2a86a8e2da22 ]---
update e820 for mtrr
modified physical RAM map:
  modified: 0000000000000000 - 0000000000001000 type 16
  modified: 0000000000001000 - 00000000000a0000 (usable)
  modified: 00000000000c0000 - 000000000fc00000 (usable)
  modified: 000000000fc00000 - 000000000fef0000 (reserved)
  modified: 000000000fef0000 - 000000000ff00000 type 16
last_pfn = 0xfc00 max_arch_pfn = 0x100000


Any ideas? Full bootlog attached.

Joseph Smith
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