[tip:x86/amd-nb] x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] exists on all future AMD CPUs

tip-bot for Andreas Herrmann
2010-10-04T20:25:44Z

Commit-ID: 3fdbf004c1706480a7c7fac3c9d836fa6df20d7d
Gitweb: http://git.kernel.org/tip/3fdbf004c1706480a7c7fac3c9d836fa6df20d7d
Author: Andreas Herrmann <andreas.herrmann3@amd.com>
AuthorDate: Thu, 30 Sep 2010 14:32:35 +0200
Committer: H. Peter Anvin <hpa@linux.intel.com>
CommitDate: Fri, 1 Oct 2010 16:18:31 -0700

x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] exists on all future AMD CPUs

Instead of adapting the CPU family check in amd_special_default_mtrr()
for each new CPU family assume that all new AMD CPUs support the
necessary bits in SYS_CFG MSR.

Tom2Enabled is architectural (defined in APM Vol.2).
Tom2ForceMemTypeWB is defined in all BKDGs starting with K8 NPT.
In pre K8-NPT BKDG this bit is reserved (read as zero).

W/o this adaption Linux would unnecessarily complain about bad MTRR
settings on every new AMD CPU family, e.g.

[ 0.000000] WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 4863MB of RAM.

Cc: stable@kernel.org # .32.x, .35.x
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20100930123235.GB20545@loge.amd.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
---
arch/x86/kernel/cpu/mtrr/cleanup.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/cleanup.c b/arch/x86/kernel/cpu/mtrr/cleanup.c
index c5f59d0..ac140c7 100644
--- a/arch/x86/kernel/cpu/mtrr/cleanup.c
+++ b/arch/x86/kernel/cpu/mtrr/cleanup.c
@@ -827,7 +827,7 @@ int __init amd_special_default_mtrr(void)

if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD)
return 0;
- if (boot_cpu_data.x86 < 0xf || boot_cpu_data.x86 > 0x11)
+ if (boot_cpu_data.x86 < 0xf)
return 0;
/* In case some hypervisor doesn't pass SYSCFG through: */
if (rdmsr_safe(MSR_K8_SYSCFG, &l, &h) < 0)