x86: remove get_cycles_sync

rdtsc is now speculation-safe, so no need for the sync variants of
the APIs.

[ mingo@elte.hu: removed the nsec_barrier() complication. ]

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 8 insertions, 52 deletions

diff --git a/include/asm-x86/tsc.h b/include/asm-x86/tsc.h
index 40130372413..f51a50da35a 100644
--- a/include/asm-x86/tsc.h
+++ b/include/asm-x86/tsc.h
@@ -36,62 +36,18 @@ static inline cycles_t get_cycles(void)
 	return ret;
 }
 
-/* Like get_cycles, but make sure the CPU is synchronized. */
-static __always_inline cycles_t __get_cycles_sync(void)
+static inline cycles_t vget_cycles(void)
 {
-	unsigned long long ret;
-	unsigned eax, edx;
-
 	/*
-	 * Use RDTSCP if possible; it is guaranteed to be synchronous
-	 * and doesn't cause a VMEXIT on Hypervisors
+	 * We only do VDSOs on TSC capable CPUs, so this shouldnt
+	 * access boot_cpu_data (which is not VDSO-safe):
 	 */
-	alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP,
-		       ASM_OUTPUT2("=a" (eax), "=d" (edx)),
-		       "a" (0U), "d" (0U) : "ecx", "memory");
-	ret = (((unsigned long long)edx) << 32) | ((unsigned long long)eax);
-	if (ret)
-		return ret;
-
-	/*
-	 * Don't do an additional sync on CPUs where we know
-	 * RDTSC is already synchronous:
-	 */
-	alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
-			  "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
-
-	return 0;
-}
-
-static __always_inline cycles_t get_cycles_sync(void)
-{
-	unsigned long long ret;
-	ret = __get_cycles_sync();
-	if (!ret)
-		rdtscll(ret);
-	return ret;
-}
-
-#ifdef CONFIG_PARAVIRT
-/*
- * For paravirt guests, some functionalities are executed through function
- * pointers in the various pvops structures.
- * These function pointers exist inside the kernel and can not
- * be accessed by user space. To avoid this, we make a copy of the
- * get_cycles_sync (called in kernel) but force the use of native_read_tsc.
- * Ideally, the guest should set up it's own clock and vread
- */
-static __always_inline long long vget_cycles_sync(void)
-{
-	unsigned long long ret;
-	ret = __get_cycles_sync();
-	if (!ret)
-		ret = native_read_tsc();
-	return ret;
-}
-#else
-# define vget_cycles_sync() get_cycles_sync()
+#ifndef CONFIG_X86_TSC
+	if (!cpu_has_tsc)
+		return 0;
 #endif
+	return (cycles_t) native_read_tsc();
+}
 
 extern void tsc_init(void);
 extern void mark_tsc_unstable(char *reason);