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>

1 files changed, 3 insertions, 8 deletions

diff --git a/arch/x86/vdso/vgetcpu.c b/arch/x86/vdso/vgetcpu.c
index 5463ad558573..2f94b039e55b 100644
--- a/arch/x86/vdso/vgetcpu.c
+++ b/arch/x86/vdso/vgetcpu.c
@@ -17,15 +17,10 @@ __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
 {
         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));
-        }
+        p = __getcpu();
+
         if (cpu)
-                *cpu = p & 0xfff;
+                *cpu = p & VGETCPU_CPU_MASK;
         if (node)
                 *node = p >> 12;
         return 0;