From 1e02ce4cccdcb9688386e5b8d2c9fa4660b45389 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Fri, 24 Oct 2014 15:58:08 -0700 Subject: x86: Store a per-cpu shadow copy of CR4 Context switches and TLB flushes can change individual bits of CR4. CR4 reads take several cycles, so store a shadow copy of CR4 in a per-cpu variable. To avoid wasting a cache line, I added the CR4 shadow to cpu_tlbstate, which is already touched in switch_mm. The heaviest users of the cr4 shadow will be switch_mm and __switch_to_xtra, and __switch_to_xtra is called shortly after switch_mm during context switch, so the cacheline is likely to be hot. Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Cc: Kees Cook Cc: Andrea Arcangeli Cc: Vince Weaver Cc: "hillf.zj" Cc: Valdis Kletnieks Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Link: http://lkml.kernel.org/r/3a54dd3353fffbf84804398e00dfdc5b7c1afd7d.1414190806.git.luto@amacapital.net Signed-off-by: Ingo Molnar --- arch/x86/power/cpu.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'arch/x86/power/cpu.c') diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c index 6ec7910..3e32ed5 100644 --- a/arch/x86/power/cpu.c +++ b/arch/x86/power/cpu.c @@ -105,11 +105,8 @@ static void __save_processor_state(struct saved_context *ctxt) ctxt->cr0 = read_cr0(); ctxt->cr2 = read_cr2(); ctxt->cr3 = read_cr3(); -#ifdef CONFIG_X86_32 - ctxt->cr4 = read_cr4_safe(); -#else -/* CONFIG_X86_64 */ - ctxt->cr4 = read_cr4(); + ctxt->cr4 = __read_cr4_safe(); +#ifdef CONFIG_X86_64 ctxt->cr8 = read_cr8(); #endif ctxt->misc_enable_saved = !rdmsrl_safe(MSR_IA32_MISC_ENABLE, @@ -175,12 +172,12 @@ static void notrace __restore_processor_state(struct saved_context *ctxt) /* cr4 was introduced in the Pentium CPU */ #ifdef CONFIG_X86_32 if (ctxt->cr4) - write_cr4(ctxt->cr4); + __write_cr4(ctxt->cr4); #else /* CONFIG X86_64 */ wrmsrl(MSR_EFER, ctxt->efer); write_cr8(ctxt->cr8); - write_cr4(ctxt->cr4); + __write_cr4(ctxt->cr4); #endif write_cr3(ctxt->cr3); write_cr2(ctxt->cr2); -- cgit v1.1