x86: vdso: pvclock gettime support
Improve performance of time system calls when using Linux pvclock,
by reading time info from fixmap visible copy of pvclock data.
Originally from Jeremy Fitzhardinge.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/include/asm/vsyscall.h b/arch/x86/include/asm/vsyscall.h
index eaea1d3..80f8095 100644
--- a/arch/x86/include/asm/vsyscall.h
+++ b/arch/x86/include/asm/vsyscall.h
@@ -33,6 +33,26 @@
*/
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 /* __KERNEL__ */
#endif /* _ASM_X86_VSYSCALL_H */