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

5b2bdbc8 · Steven Rostedt <[email protected]> · 2015-02-27 14:50:19 -05:00

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/[email protected] Fixes: 1e02ce4cccdc "x86: Store a per-cpu shadow copy of CR4"
Signed-off-by: Steven Rostedt <[email protected]>
Acked-by: Andy Lutomirski <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Linus Torvalds <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Commit: 5b2bdbc84556774afbe11bcfd24c2f6411cfa92b
Parents: 5838d189

Changes

1 files changed · +6 −0

File	Status	Add	Del	Content
arch/x86/kernel/cpu/common.c	modified	+6	−0	View file

arch/x86/kernel/cpu/common.c

View file

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);