linux-kernel - [PATCH] x86/amd: disable way access filter on affected CPUs

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Message-ID: <1351065377-1989-1-git-send-email-andre.przywara@amd.com>
Date:	Wed, 24 Oct 2012 09:56:17 +0200
From:	Andre Przywara <andre.przywara@....com>
To:	<hpa@...or.com>, <tglx@...utronix.de>, <mingo@...e.hu>
CC:	<linux-kernel@...r.kernel.org>, <andreas.herrmann3@....com>,
	Andre Przywara <andre.przywara@....com>
Subject: [PATCH] x86/amd: disable way access filter on affected CPUs

The WAF may hurt the performance of some workloads, caused by
aliasing issues in the L1 cache.
Disable it on the affected CPUs.

Signed-off-by: Andre Przywara <andre.przywara@....com>
---
 arch/x86/kernel/cpu/amd.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index f7e98a2..1b7d165 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -631,6 +631,20 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 		}
 	}
 
+	/*
+	 * The way access filter has a performance penalty on some workloads.
+	 * Disable it on the affected CPUs.
+	 */
+	if ((c->x86 == 0x15) &&
+	    (c->x86_model >= 0x02) && (c->x86_model < 0x20)) {
+		u64 val;
+
+		if (!rdmsrl_safe(0xc0011021, &val) && !(val & 0x1E)) {
+			val |= 0x1E;
+			wrmsrl_safe(0xc0011021, val);
+		}
+	}
+
 	cpu_detect_cache_sizes(c);
 
 	/* Multi core CPU? */
-- 
1.7.12.1


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