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authorAndy Lutomirski <luto@amacapital.net>2014-10-25 02:58:08 +0400
committerIngo Molnar <mingo@kernel.org>2015-02-04 14:10:42 +0300
commit1e02ce4cccdcb9688386e5b8d2c9fa4660b45389 (patch)
tree7d514286844acea505228590119ac1a886cf6995 /arch/x86/power
parent375074cc736ab1d89a708c0a8d7baa4a70d5d476 (diff)
downloadlinux-1e02ce4cccdcb9688386e5b8d2c9fa4660b45389.tar.xz
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 <luto@amacapital.net> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Kees Cook <keescook@chromium.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Vince Weaver <vince@deater.net> Cc: "hillf.zj" <hillf.zj@alibaba-inc.com> Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu> Cc: Paul Mackerras <paulus@samba.org> Cc: Arnaldo Carvalho de Melo <acme@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: http://lkml.kernel.org/r/3a54dd3353fffbf84804398e00dfdc5b7c1afd7d.1414190806.git.luto@amacapital.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/power')
-rw-r--r--arch/x86/power/cpu.c11
1 files changed, 4 insertions, 7 deletions
diff --git a/arch/x86/power/cpu.c b/arch/x86/power/cpu.c
index 6ec7910f59bf..3e32ed5648a0 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);