x86: introduce native_read_tscp

Targetting paravirt, this patch introduces native_read_tscp, in
place of rdtscp() macro. When in a paravirt guest, this will
involve a function call, and thus, cannot be done in the vdso area.
These users then have to call the native version directly

Signed-off-by: Glauber de Oliveira Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

3 files changed, 25 insertions, 12 deletions

diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 018f7cf33790..c4c5e765cd2c 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -190,7 +190,7 @@ time_t __vsyscall(1) vtime(time_t *t)
 long __vsyscall(2)
 vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
 {
-        unsigned int dummy, p;
+        unsigned int p;
         unsigned long j = 0;
 
         /* Fast cache - only recompute value once per jiffies and avoid
@@ -205,7 +205,7 @@ vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache)
                 p = tcache->blob[1];
         } else if (__vgetcpu_mode == VGETCPU_RDTSCP) {
                 /* Load per CPU data from RDTSCP */
-                rdtscp(dummy, dummy, p);
+                native_read_tscp(&p);
         } else {
                 /* Load per CPU data from GDT */
                 asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
diff --git a/arch/x86/vdso/vgetcpu.c b/arch/x86/vdso/vgetcpu.c
index 3b1ae1abfba9..c8097f17f8a9 100644
--- a/arch/x86/vdso/vgetcpu.c
+++ b/arch/x86/vdso/vgetcpu.c
@@ -15,11 +15,11 @@
 
 long __vdso_getcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *unused)
 {
-        unsigned int dummy, p;
+        unsigned int p;
 
         if (*vdso_vgetcpu_mode == VGETCPU_RDTSCP) {
                 /* Load per CPU data from RDTSCP */
-                rdtscp(dummy, dummy, p);
+                native_read_tscp(&p);
         } else {
                 /* Load per CPU data from GDT */
                 asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG));
diff --git a/include/asm-x86/msr.h b/include/asm-x86/msr.h
index 0648b2d57a38..b6262e99fc8e 100644
--- a/include/asm-x86/msr.h
+++ b/include/asm-x86/msr.h
@@ -7,6 +7,27 @@
 # include <linux/types.h>
 #endif
 
+#ifdef __KERNEL__
+#ifndef __ASSEMBLY__
+static inline unsigned long long native_read_tscp(int *aux)
+{
+        unsigned long low, high;
+        asm volatile (".byte 0x0f,0x01,0xf9"
+                      : "=a" (low), "=d" (high), "=c" (*aux));
+        return low | ((u64)high >> 32);
+}
+
+#define rdtscp(low, high, aux)                                          \
+       do {                                                            \
+                unsigned long long _val = native_read_tscp(&(aux));     \
+                (low) = (u32)_val;                                      \
+                (high) = (u32)(_val >> 32);                             \
+       } while (0)
+
+#define rdtscpll(val, aux) (val) = native_read_tscp(&(aux))
+#endif
+#endif
+
 #ifdef __i386__
 
 #ifdef __KERNEL__
@@ -178,8 +199,6 @@ static inline int wrmsr_safe(u32 __msr, u32 __low, u32 __high)
 #define rdtscl(low) \
      __asm__ __volatile__ ("rdtsc" : "=a" (low) : : "edx")
 
-#define rdtscp(low,high,aux) \
-     __asm__ __volatile__ (".byte 0x0f,0x01,0xf9" : "=a" (low), "=d" (high), "=c" (aux))
 
 #define rdtscll(val) do { \
      unsigned int __a,__d; \
@@ -187,12 +206,6 @@ static inline int wrmsr_safe(u32 __msr, u32 __low, u32 __high)
      (val) = ((unsigned long)__a) | (((unsigned long)__d)<<32); \
 } while(0)
 
-#define rdtscpll(val, aux) do { \
-     unsigned long __a, __d; \
-     __asm__ __volatile__ (".byte 0x0f,0x01,0xf9" : "=a" (__a), "=d" (__d), "=c" (aux)); \
-     (val) = (__d << 32) | __a; \
-} while (0)
-
 #define write_tsc(val1,val2) wrmsr(0x10, val1, val2)
 
 #define write_rdtscp_aux(val) wrmsr(0xc0000103, val, 0)