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x86,vdso: Use LSL unconditionally for vgetcpu

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LSL is faster than RDTSCP and works everywhere; there's no need to
switch between them depending on CPU.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <andi@firstfloor.org>
Link: http://lkml.kernel.org/r/72f73d5ec4514e02bba345b9759177ef03742efb.1414706021.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Andy Lutomirski
2014-10-30 14:58:01 -07:00
committed by Thomas Gleixner
parent a92f101bc9
commit e76b027e64
6 changed files with 19 additions and 43 deletions
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19
arch/x86/include/asm/vgtod.h
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@@ -70,4 +70,23 @@ static inline void gtod_write_end(struct vsyscall_gtod_data *s)
++s->seq;
}
#ifdef CONFIG_X86_64
#define VGETCPU_CPU_MASK 0xfff
static inline unsigned int __getcpu(void)
{
unsigned int p;
/*
* Load per CPU data from GDT. LSL is faster than RDTSCP and
* works on all CPUs.
*/
asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
return p;
}
#endif /* CONFIG_X86_64 */
#endif /* _ASM_X86_VGTOD_H */