[PATCH 1/6] x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] existson all future AMD CPUs

[Andreas Herrmann]

From: Andreas Herrmann <andreas.herrmann3@xxxxxxx>

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@xxxxxxxxxx # .32.x, .35.x
Signed-off-by: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
---
 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)
-- 
1.6.4.4

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