x86/mm: If INVPCID is available, use it to flush global mappings

On my Skylake laptop, INVPCID function 2 (flush absolutely
everything) takes about 376ns, whereas saving flags, twiddling
CR4.PGE to flush global mappings, and restoring flags takes about
539ns.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Toshi Kani <toshi.kani@hp.com>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/ed0ef62581c0ea9c99b9bf6df726015e96d44743.1454096309.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 8b576832777e2c81b87eda925c125a19863618f4..fc9a2fda14040d083e01052a5b69163d4ddac8cf 100644 (file)
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -152,6 +152,15 @@ static inline void __native_flush_tlb_global(void)
 {
        unsigned long flags;
 
+       if (static_cpu_has(X86_FEATURE_INVPCID)) {
+               /*
+                * Using INVPCID is considerably faster than a pair of writes
+                * to CR4 sandwiched inside an IRQ flag save/restore.
+                */
+               invpcid_flush_all();
+               return;
+       }
+
        /*
         * Read-modify-write to CR4 - protect it from preemption and
         * from interrupts. (Use the raw variant because this code can