diff options
| author | Andy Lutomirski <luto@kernel.org> | 2016-11-16 10:23:27 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-11-17 08:31:14 +0100 |
| commit | a582c540ac1b10f0a7d37415e04c4af42409fd08 (patch) | |
| tree | 7aa03d7e392b1f08fea2719e66b536113e40c2e7 | |
| parent | 89a01c51cbe3b6ae81008e8c91235be583df8c50 (diff) | |
x86/vdso: Use RDPID in preference to LSL when available
RDPID is a new instruction that reads MSR_TSC_AUX quickly. This
should be considerably faster than reading the GDT. Add a
cpufeature for it and use it from __vdso_getcpu() when available.
Tested-by: Megha Dey <megha.dey@intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/4f6c3a22012d10f1c65b9ca15800e01b42c7d39d.1479320367.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 1 | ||||
| -rw-r--r-- | arch/x86/include/asm/vgtod.h | 7 |
2 files changed, 7 insertions, 1 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index a3e8cd762a23..eac7572bf8bb 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -283,6 +283,7 @@ #define X86_FEATURE_AVX512VBMI (16*32+ 1) /* AVX512 Vector Bit Manipulation instructions*/ #define X86_FEATURE_PKU (16*32+ 3) /* Protection Keys for Userspace */ #define X86_FEATURE_OSPKE (16*32+ 4) /* OS Protection Keys Enable */ +#define X86_FEATURE_RDPID (16*32+ 22) /* RDPID instruction */ /* AMD-defined CPU features, CPUID level 0x80000007 (ebx), word 17 */ #define X86_FEATURE_OVERFLOW_RECOV (17*32+0) /* MCA overflow recovery support */ diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h index e728699db774..3a01996db58f 100644 --- a/arch/x86/include/asm/vgtod.h +++ b/arch/x86/include/asm/vgtod.h @@ -89,8 +89,13 @@ static inline unsigned int __getcpu(void) * works on all CPUs. This is volatile so that it orders * correctly wrt barrier() and to keep gcc from cleverly * hoisting it out of the calling function. + * + * If RDPID is available, use it. */ - asm volatile ("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); + alternative_io ("lsl %[p],%[seg]", + ".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */ + X86_FEATURE_RDPID, + [p] "=a" (p), [seg] "r" (__PER_CPU_SEG)); return p; } |