linux-kernel - [PATCH 4.4 025/118] x86/AMD: Apply erratum 665 on machines without a BIOS fix

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Date:   Thu, 22 Sep 2016 19:28:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Emanuel Czirai <icanrealizeum@...il.com>,
        Borislav Petkov <bp@...e.de>, Yaowu Xu <yaowu@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 4.4 025/118] x86/AMD: Apply erratum 665 on machines without a BIOS fix

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Emanuel Czirai <icanrealizeum@...il.com>

commit d1992996753132e2dafe955cccb2fb0714d3cfc4 upstream.

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>
Link: http://lkml.kernel.org/r/20160902053550.18097-1-bp@alien8.de
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -656,6 +656,17 @@ static void init_amd_gh(struct cpuinfo_x
 		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;
@@ -713,6 +724,7 @@ static void init_amd(struct cpuinfo_x86
 	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;
 	}