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x86,vdso: Use LSL unconditionally for vgetcpu 

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
View File

@ -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 */

29
arch/x86/include/asm/vsyscall.h
View File

@ -4,15 +4,6 @@
#include <linux/seqlock.h>
#include <uapi/asm/vsyscall.h>
#define VGETCPU_RDTSCP 1
#define VGETCPU_LSL 2
/* kernel space (writeable) */
extern int vgetcpu_mode;
extern struct timezone sys_tz;
#include <asm/vvar.h>
extern void map_vsyscall(void);
/*
@ -21,24 +12,4 @@ extern void map_vsyscall(void);
*/
extern bool emulate_vsyscall(struct pt_regs *regs, unsigned long address);
#ifdef CONFIG_X86_64
#define VGETCPU_CPU_MASK 0xfff
static inline unsigned int __getcpu(void)
{
unsigned int p;
if (VVAR(vgetcpu_mode) == VGETCPU_RDTSCP) {
/* Load per CPU data from RDTSCP */
native_read_tscp(&p);
} else {
/* Load per CPU data from GDT */
asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
}
return p;
}
#endif /* CONFIG_X86_64 */
#endif /* _ASM_X86_VSYSCALL_H */

1
arch/x86/include/asm/vvar.h
View File

@ -44,7 +44,6 @@ extern char __vvar_page;
/* DECLARE_VVAR(offset, type, name) */
DECLARE_VVAR(16, int, vgetcpu_mode)
DECLARE_VVAR(128, struct vsyscall_gtod_data, vsyscall_gtod_data)
#undef DECLARE_VVAR

10
arch/x86/kernel/cpu/common.c
View File

@ -956,14 +956,6 @@ static void identify_cpu(struct cpuinfo_x86 *c)
}
#ifdef CONFIG_X86_64
static void vgetcpu_set_mode(void)
{
if (cpu_has(&boot_cpu_data, X86_FEATURE_RDTSCP))
vgetcpu_mode = VGETCPU_RDTSCP;
else
vgetcpu_mode = VGETCPU_LSL;
}
#ifdef CONFIG_IA32_EMULATION
/* May not be __init: called during resume */
static void syscall32_cpu_init(void)
@ -1006,8 +998,6 @@ void __init identify_boot_cpu(void)
#ifdef CONFIG_X86_32
sysenter_setup();
enable_sep_cpu();
#else
vgetcpu_set_mode();
#endif
cpu_detect_tlb(&boot_cpu_data);
}

2
arch/x86/kernel/vsyscall_64.c
View File

@ -52,8 +52,6 @@
#define CREATE_TRACE_POINTS
#include "vsyscall_trace.h"
DEFINE_VVAR(int, vgetcpu_mode);
static enum { EMULATE, NATIVE, NONE } vsyscall_mode = EMULATE;
static int __init vsyscall_setup(char *str)

1
arch/x86/vdso/vgetcpu.c
View File

@ -8,7 +8,6 @@
#include <linux/kernel.h>
#include <linux/getcpu.h>
#include <linux/time.h>
#include <asm/vsyscall.h>
#include <asm/vgtod.h>
notrace long