linux-kernel - [PATCH] x86: amd k6-2 mtrr not detected fix

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Message-Id: <20080831155828.d7dd0a76.krzysztof.h1@wp.pl>
Date:	Sun, 31 Aug 2008 15:58:28 +0200
From:	Krzysztof Helt <krzysztof.h1@...pl>
To:	linux-kernel@...r.kernel.org
Cc:	hpa@...or.com, tglx@...utronix.de, mingo@...hat.com
Subject: [PATCH] x86: amd k6-2 mtrr not detected fix

From: Krzysztof Helt <krzysztof.h1@...pl>

The AMD K6-2 cpus have 2 mtrr registers 
which are not detected by the latest Linux
kernel.
The mtrr capability is not reported through
the cpuid on these cpus. This fools early
detection function [mtrr_bp_init()] as the
mtrr capability bit is set later in
the init_amd() function.
Fix it by setting the K6 mtrr capability bit
just before the check in mtrr_bp_init().
The added condition is copied from the init_amd().

Signed-off-by: Krzysztof Helt <krzysztof.h1@...pl>
---

It seems that the same problem affects Cyrix and
Centaur/VIA cpus. Can some x86 guy inspect the
mtrr initialization code ?

 arch/x86/kernel/cpu/mtrr/main.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 58ac5d3..4bef914 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -1612,6 +1612,12 @@ void __init mtrr_bp_init(void)
 	} else {
 		switch (boot_cpu_data.x86_vendor) {
 		case X86_VENDOR_AMD:
+			if (boot_cpu_data.x86_model == 13 ||
+			    boot_cpu_data.x86_model == 9 ||
+			    (boot_cpu_data.x86_model == 8 &&
+			     boot_cpu_data.x86_mask >= 8))
+				set_cpu_cap(&boot_cpu_data,
+					    X86_FEATURE_K6_MTRR);
 			if (cpu_has_k6_mtrr) {
 				/* Pre-Athlon (K6) AMD CPU MTRRs */
 				mtrr_if = mtrr_ops[X86_VENDOR_AMD];
-- 
1.5.2.2

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