On Fri, 27 Feb 2015 10:59:52 -0800 Linus Torvalds <[email protected]> wrote: > Presumably there is some initialization missing - I suspect that the > cached value of cr4 is from the *previous* time the CPU was up, and we > don't correctly initialize the cached copy at early CPU bringup.
Found it. The problem is that there's two cpu_init()s in common.c. Andy only added the cr4 init to one of them. x86: Init per-cpu shadow copy of CR4 for i386 too The 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 x86_64 and one for i386. The commit only added the shadow init to x86_64. The i386 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]> --- 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); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
