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Old 06-03-2008, 11:35 PM
Alok Kataria
 
Default x86: remove get_cycles_sync

OriginalAuthor: Andi Kleen <ak@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@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




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