linux-kernel - [PATCH] x86_32: Initialize the cr4 shadow on cpu init

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Date:	Fri, 27 Feb 2015 11:53:39 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Steven Rostedt <rostedt@...dmis.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Cc:	Andy Lutomirski <luto@...capital.net>
Subject: [PATCH] x86_32: Initialize the cr4 shadow on cpu init

32-bit secondary cpus had uninitialized cr4 shadows, causing random
failures.

Reported-by: Steven Rostedt <rostedt@...dmis.org>
Signed-off-by: Andy Lutomirski <luto@...capital.net>
---

This is embarrassing.  I must have gotten lucky testing it.

arch/x86/kernel/cpu/common.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index b5c8ff5e9dfc..2346c95c6ab1 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1396,6 +1396,12 @@ void cpu_init(void)
 
 	wait_for_master_cpu(cpu);
 
+	/*
+	 * Initialize the CR4 shadow before doing anything that could
+	 * try to read it.
+	 */
+	cr4_init_shadow();
+
 	show_ucode_info_early();
 
 	printk(KERN_INFO "Initializing CPU#%d\n", cpu);
-- 
2.1.0

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