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Commit 6d63de8d authored by Andi Kleen's avatar Andi Kleen Committed by Ingo Molnar
Browse files

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: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent f06e4ec1

arch/x86/kernel/time_64.c

+1 −1
Original line number Diff line number Diff line
@@ -83,7 +83,7 @@ unsigned long __init native_calculate_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);

arch/x86/kernel/tsc_64.c

+6 −6
Original line number Diff line number Diff line
@@ -181,12 +181,12 @@ 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;

	}
@@ -210,9 +210,9 @@ 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);
@@ -300,13 +300,13 @@ __setup("notsc", notsc_setup); 
/* clock source code: */

static cycle_t read_tsc(void)

{

	cycle_t ret = (cycle_t)get_cycles_sync();

	cycle_t ret = (cycle_t)get_cycles();

	return ret;

}



static cycle_t __vsyscall_fn vread_tsc(void)

{

	cycle_t ret = (cycle_t)vget_cycles_sync();

	cycle_t ret = (cycle_t)vget_cycles();

	return ret;

}

arch/x86/kernel/tsc_sync.c

+2 −2
Original line number Diff line number Diff line
@@ -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);

include/asm-x86/tsc.h

+8 −52
Original line number Diff line number Diff line
@@ -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

	 */

	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");



#ifndef CONFIG_X86_TSC

	if (!cpu_has_tsc)

		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()

#endif

	return (cycles_t) native_read_tsc();

}



extern void tsc_init(void);

extern void mark_tsc_unstable(char *reason);