linux-kernel - [tip:x86/urgent] x86: Init per-cpu shadow copy of CR4 on 32-bit CPUs too

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Date:	Fri, 27 Feb 2015 23:07:00 -0800
From:	tip-bot for Steven Rostedt <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	tglx@...utronix.de, torvalds@...ux-foundation.org,
	luto@...capital.net, peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org, rostedt@...dmis.org, hpa@...or.com
Subject: [tip:x86/urgent] x86:
  Init per-cpu shadow copy of CR4 on 32-bit CPUs too

Commit-ID:  5b2bdbc84556774afbe11bcfd24c2f6411cfa92b
Gitweb:     http://git.kernel.org/tip/5b2bdbc84556774afbe11bcfd24c2f6411cfa92b
Author:     Steven Rostedt <rostedt@...dmis.org>
AuthorDate: Fri, 27 Feb 2015 14:50:19 -0500
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Sat, 28 Feb 2015 08:04:20 +0100

x86: Init per-cpu shadow copy of CR4 on 32-bit CPUs too

Commit:

   1e02ce4cccdc ("x86: Store a per-cpu shadow copy of CR4")

added a shadow CR4 such that reads and writes that do not
modify the CR4 execute much faster than always reading the
register itself.

The change modified cpu_init() in common.c, so that the
shadow CR4 gets initialized before anything uses it.

Unfortunately, there's two cpu_init()s in common.c. There's
one for 64-bit and one for 32-bit. The commit only added
the shadow init to the 64-bit path, but the 32-bit path
needs the init too.

Link: http://lkml.kernel.org/r/20150227125208.71c36402@gandalf.local.home Fixes: 1e02ce4cccdc "x86: Store a per-cpu shadow copy of CR4"
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
Acked-by: Andy Lutomirski <luto@...capital.net>
Cc: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Link: http://lkml.kernel.org/r/20150227145019.2bdd4354@gandalf.local.home
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 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 b5c8ff5..2346c95 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);
--
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