[PATCH 5/6] x86: remove get_cycles_sync

[Alok Kataria]

OriginalAuthor: Andi Kleen <ak at suse.de>
Commit: 6d63de8dbcda98511206897562ecfcdacf18f523

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

Signed-off-by: Alok N Kataria <akataria at vmware.com>
---
 arch/x86/kernel/time_64.c  |    2 +-
 arch/x86/kernel/tsc_64.c   |   12 ++++++------
 arch/x86/kernel/tsc_sync.c |    4 ++--
 include/asm-x86/tsc.h      |   31 ++++++++-----------------------
 4 files changed, 17 insertions(+), 32 deletions(-)

diff --git a/arch/x86/kernel/time_64.c b/arch/x86/kernel/time_64.c
index 368b194..95b995e 100644
--- a/arch/x86/kernel/time_64.c
+++ b/arch/x86/kernel/time_64.c
@@ -241,7 +241,7 @@ static unsigned int __init tsc_calibrate_cpu_khz(void)
 	rdtscl(tsc_start);
 	do {
 		rdmsrl(MSR_K7_PERFCTR0 + i, pmc_now);
-		tsc_now = get_cycles_sync();
+		tsc_now = get_cycles();
 	} while ((tsc_now - tsc_start) < TICK_COUNT);
 
 	local_irq_restore(flags);
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c
index 2b1e1bc..0b28712 100644
--- a/arch/x86/kernel/tsc_64.c
+++ b/arch/x86/kernel/tsc_64.c
@@ -134,12 +134,12 @@ static unsigned long __init tsc_read_refs(unsigned long *pm,
 	int i;
 
 	for (i = 0; i < MAX_RETRIES; i++) {
-		t1 = get_cycles_sync();
+		t1 = get_cycles();
 		if (hpet)
 			*hpet = hpet_readl(HPET_COUNTER) & 0xFFFFFFFF;
 		else
 			*pm = acpi_pm_read_early();
-		t2 = get_cycles_sync();
+		t2 = get_cycles();
 		if ((t2 - t1) < SMI_TRESHOLD)
 			return t2;
 	}
@@ -163,9 +163,9 @@ void __init tsc_calibrate(void)
 	outb(0xb0, 0x43);
 	outb((CLOCK_TICK_RATE / (1000 / 50)) & 0xff, 0x42);
 	outb((CLOCK_TICK_RATE / (1000 / 50)) >> 8, 0x42);
-	tr1 = get_cycles_sync();
+	tr1 = get_cycles();
 	while ((inb(0x61) & 0x20) == 0);
-	tr2 = get_cycles_sync();
+	tr2 = get_cycles();
 
 	tsc2 = tsc_read_refs(&pm2, hpet ? &hpet2 : NULL);
 
@@ -263,7 +263,7 @@ static struct clocksource clocksource_tsc;
  */
 static cycle_t read_tsc(void)
 {
-	cycle_t ret = (cycle_t)get_cycles_sync();
+	cycle_t ret = (cycle_t)get_cycles();
 
 	return ret >= clocksource_tsc.cycle_last ?
 		ret : clocksource_tsc.cycle_last;
@@ -271,7 +271,7 @@ static cycle_t read_tsc(void)
 
 static cycle_t __vsyscall_fn vread_tsc(void)
 {
-	cycle_t ret = (cycle_t)get_cycles_sync();
+	cycle_t ret = (cycle_t)vget_cycles();
 
 	return ret >= __vsyscall_gtod_data.clock.cycle_last ?
 		ret : __vsyscall_gtod_data.clock.cycle_last;
diff --git a/arch/x86/kernel/tsc_sync.c b/arch/x86/kernel/tsc_sync.c
index 9125efe..28cabf8 100644
--- a/arch/x86/kernel/tsc_sync.c
+++ b/arch/x86/kernel/tsc_sync.c
@@ -46,7 +46,7 @@ static __cpuinit void check_tsc_warp(void)
 	cycles_t start, now, prev, end;
 	int i;
 
-	start = get_cycles_sync();
+	start = get_cycles();
 	/*
 	 * The measurement runs for 20 msecs:
 	 */
@@ -61,7 +61,7 @@ static __cpuinit void check_tsc_warp(void)
 		 */
 		__raw_spin_lock(&sync_lock);
 		prev = last_tsc;
-		now = get_cycles_sync();
+		now = get_cycles();
 		last_tsc = now;
 		__raw_spin_unlock(&sync_lock);
 
diff --git a/include/asm-x86/tsc.h b/include/asm-x86/tsc.h
index 6baab30..8ca7242 100644
--- a/include/asm-x86/tsc.h
+++ b/include/asm-x86/tsc.h
@@ -32,32 +32,17 @@ 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
-	 */
-	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:
+	 * We only do VDSOs on TSC capable CPUs, so this shouldnt
+	 * access boot_cpu_data (which is not VDSO-safe):
 	 */
-	alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
-			  "=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
-	rdtscll(ret);
-
-	return ret;
+#ifndef CONFIG_X86_TSC
+	if (!cpu_has_tsc)
+		return 0;
+#endif
+	return (cycles_t) native_read_tsc();
 }
 
 extern void tsc_init(void);
-- 
1.5.4