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Commit e76b027e authored by Andy Lutomirski's avatar Andy Lutomirski Committed by Thomas Gleixner
Browse files

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: default avatarAndy 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: default avatarThomas Gleixner <tglx@linutronix.de>
parent a92f101b

arch/x86/include/asm/vgtod.h

+19 −0
Original line number Diff line number Diff line
@@ -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 */

arch/x86/include/asm/vsyscall.h

+0 −29
Original line number Diff line number Diff line
@@ -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 */

arch/x86/include/asm/vvar.h

+0 −1
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/cpu/common.c

+0 −10
Original line number Diff line number Diff line
@@ -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);

}

arch/x86/kernel/vsyscall_64.c

+0 −2
Original line number Diff line number Diff line
@@ -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)