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>

6 files changed, 19 insertions, 43 deletions

diff --git a/arch/x86/include/asm/vgtod.h b/arch/x86/include/asm/vgtod.h
index 3c3366c2e37f..e7e9682a33e9 100644
--- a/arch/x86/include/asm/vgtod.h
+++ b/arch/x86/include/asm/vgtod.h
@@ -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 */
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index 2a46ca720afc..34f7d8857542 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -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 */
diff --git a/arch/x86/include/asm/vvar.h b/arch/x86/include/asm/vvar.h
index 5f6d40734a3b..3f32dfc2ab73 100644
--- a/arch/x86/include/asm/vvar.h
+++ b/arch/x86/include/asm/vvar.h
@@ -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
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 4b4f78c9ba19..175372b854be 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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);
 }
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 2f9ef0c1d112..419e83b58436 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -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)
diff --git a/arch/x86/vdso/vgetcpu.c b/arch/x86/vdso/vgetcpu.c
index add1d98d2477..8ec3d1f4ce9a 100644
--- a/arch/x86/vdso/vgetcpu.c
+++ b/arch/x86/vdso/vgetcpu.c
@@ -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