linux-kernel - [PATCH] Don't enable F00F workaround on Intel Quark processors.

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Message-ID: <20141028175753.GA12743@redhat.com>
Date:	Tue, 28 Oct 2014 13:57:53 -0400
From:	Dave Jones <davej@...hat.com>
To:	Linux Kernel <linux-kernel@...r.kernel.org>
Cc:	x86@...nel.org, "Bryan O'Donoghue" <pure.logic@...us-software.ie>
Subject: [PATCH] Don't enable F00F workaround on Intel Quark processors.

The Intel Quark processor is a part of family 5, but does not have the
F00F bug present in Pentiums of the same family.

Pentiums were models 0 through 8, Quark is model 9.

Cc: Bryan O'Donoghue <pure.logic@...us-software.ie>
Signed-off-by: Dave Jones <davej@...hat.com>

diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index 1ef456273172..9cc6b6f25f42 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -213,12 +213,13 @@ static void intel_workarounds(struct cpuinfo_x86 *c)
 {
 #ifdef CONFIG_X86_F00F_BUG
 	/*
-	 * All current models of Pentium and Pentium with MMX technology CPUs
+	 * All models of Pentium and Pentium with MMX technology CPUs
 	 * have the F0 0F bug, which lets nonprivileged users lock up the
 	 * system. Announce that the fault handler will be checking for it.
+	 * The Quark is also family 5, but does not have the same bug.
 	 */
 	clear_cpu_bug(c, X86_BUG_F00F);
-	if (!paravirt_enabled() && c->x86 == 5) {
+	if (!paravirt_enabled() && c->x86 == 5 && c->x86_model < 9) {
 		static int f00f_workaround_enabled;
 
 		set_cpu_bug(c, X86_BUG_F00F);
--
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