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

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Message-ID: <tip-3fdbf004c1706480a7c7fac3c9d836fa6df20d7d@git.kernel.org>
Date:	Mon, 4 Oct 2010 20:25:25 GMT
From:	tip-bot for Andreas Herrmann <andreas.herrmann3@....com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	andreas.herrmann3@....com, tglx@...utronix.de, hpa@...ux.intel.com
Subject: [tip:x86/amd-nb] x86, mtrr: Assume SYS_CFG[Tom2ForceMemTypeWB] exists on all future AMD CPUs

Commit-ID:  3fdbf004c1706480a7c7fac3c9d836fa6df20d7d
Gitweb:     http://git.kernel.org/tip/3fdbf004c1706480a7c7fac3c9d836fa6df20d7d
Author:     Andreas Herrmann <andreas.herrmann3@....com>
AuthorDate: Thu, 30 Sep 2010 14:32:35 +0200
Committer:  H. Peter Anvin <hpa@...ux.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@...nel.org # .32.x, .35.x
Signed-off-by: Andreas Herrmann <andreas.herrmann3@....com>
LKML-Reference: <20100930123235.GB20545@...e.amd.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.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)
--
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