linux-kernel - [tip:x86/urgent] x86/AMD: Apply erratum 665 on machines without a BIOS fix

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Date:   Fri, 2 Sep 2016 12:37:11 -0700
From:   tip-bot for Emanuel Czirai <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     bp@...e.de, hpa@...or.com, icanrealizeum@...il.com,
        mingo@...nel.org, tglx@...utronix.de, linux-kernel@...r.kernel.org,
        yaowu@...gle.com
Subject: [tip:x86/urgent] x86/AMD: Apply erratum 665 on machines without a
 BIOS fix

Commit-ID:  d1992996753132e2dafe955cccb2fb0714d3cfc4
Gitweb:     http://git.kernel.org/tip/d1992996753132e2dafe955cccb2fb0714d3cfc4
Author:     Emanuel Czirai <icanrealizeum@...il.com>
AuthorDate: Fri, 2 Sep 2016 07:35:50 +0200
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Fri, 2 Sep 2016 20:42:28 +0200

x86/AMD: Apply erratum 665 on machines without a BIOS fix

AMD F12h machines have an erratum which can cause DIV/IDIV to behave
unpredictably. The workaround is to set MSRC001_1029[31] but sometimes
there is no BIOS update containing that workaround so let's do it
ourselves unconditionally. It is simple enough.

[ Borislav: Wrote commit message. ]

Signed-off-by: Emanuel Czirai <icanrealizeum@...il.com>
Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Yaowu Xu <yaowu@...gle.com>
Cc: stable@...r.kernel.org
Link: http://lkml.kernel.org/r/20160902053550.18097-1-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/kernel/cpu/amd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index f5c69d8..b81fe2d 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -669,6 +669,17 @@ static void init_amd_gh(struct cpuinfo_x86 *c)
 		set_cpu_bug(c, X86_BUG_AMD_TLB_MMATCH);
 }
 
+#define MSR_AMD64_DE_CFG	0xC0011029
+
+static void init_amd_ln(struct cpuinfo_x86 *c)
+{
+	/*
+	 * Apply erratum 665 fix unconditionally so machines without a BIOS
+	 * fix work.
+	 */
+	msr_set_bit(MSR_AMD64_DE_CFG, 31);
+}
+
 static void init_amd_bd(struct cpuinfo_x86 *c)
 {
 	u64 value;
@@ -726,6 +737,7 @@ static void init_amd(struct cpuinfo_x86 *c)
 	case 6:	   init_amd_k7(c); break;
 	case 0xf:  init_amd_k8(c); break;
 	case 0x10: init_amd_gh(c); break;
+	case 0x12: init_amd_ln(c); break;
 	case 0x15: init_amd_bd(c); break;
 	}