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Commit 3e2d9453 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Thomas Gleixner
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clocksource/drivers/hyperv: Enable TSC page clocksource on 32bit 



There is no particular reason to not enable TSC page clocksource on
32-bit. mul_u64_u64_shr() is available and despite the increased
computational complexity (compared to 64bit) TSC page is still a huge win
compared to MSR-based clocksource.

In-kernel reads:
  MSR based clocksource: 3361 cycles
  TSC page clocksource: 49 cycles

Reads from userspace (utilizing vDSO in case of TSC page):
  MSR based clocksource: 5664 cycles
  TSC page clocksource: 131 cycles

Enabling TSC page on 32bits allows to get rid of CONFIG_HYPERV_TSCPAGE as
it is now not any different from CONFIG_HYPERV_TIMER.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarMichael Kelley <mikelley@microsoft.com>
Link: https://lkml.kernel.org/r/20190822083630.17059-1-vkuznets@redhat.com
parent bd00cd52

arch/x86/include/asm/vdso/gettimeofday.h

+3 −3
Original line number Diff line number Diff line
@@ -51,7 +51,7 @@ extern struct pvclock_vsyscall_time_info pvclock_page 
	__attribute__((visibility("hidden")));

#endif



#ifdef CONFIG_HYPERV_TSCPAGE

#ifdef CONFIG_HYPERV_TIMER

extern struct ms_hyperv_tsc_page hvclock_page

	__attribute__((visibility("hidden")));

#endif
@@ -192,7 +192,7 @@ static u64 vread_pvclock(void) 
}

#endif



#ifdef CONFIG_HYPERV_TSCPAGE

#ifdef CONFIG_HYPERV_TIMER

static u64 vread_hvclock(void)

{

	return hv_read_tsc_page(&hvclock_page);
@@ -215,7 +215,7 @@ static inline u64 __arch_get_hw_counter(s32 clock_mode) 
		return vread_pvclock();

	}

#endif

#ifdef CONFIG_HYPERV_TSCPAGE

#ifdef CONFIG_HYPERV_TIMER

	if (clock_mode == VCLOCK_HVCLOCK) {

		barrier();

		return vread_hvclock();

drivers/clocksource/hyperv_timer.c

+0 −11
Original line number Diff line number Diff line
@@ -213,8 +213,6 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup); 
struct clocksource *hyperv_cs;

EXPORT_SYMBOL_GPL(hyperv_cs);



#ifdef CONFIG_HYPERV_TSCPAGE



static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);



struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
@@ -245,7 +243,6 @@ static struct clocksource hyperv_cs_tsc = { 
	.mask	= CLOCKSOURCE_MASK(64),

	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,

};

#endif



static u64 notrace read_hv_clock_msr(struct clocksource *arg)

{
@@ -272,7 +269,6 @@ static struct clocksource hyperv_cs_msr = { 
	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,

};



#ifdef CONFIG_HYPERV_TSCPAGE

static bool __init hv_init_tsc_clocksource(void)

{

	u64		tsc_msr;
@@ -304,13 +300,6 @@ static bool __init hv_init_tsc_clocksource(void) 


	return true;

}

#else

static bool __init hv_init_tsc_clocksource(void)

{

	return false;

}

#endif





void __init hv_init_clocksource(void)

{

drivers/hv/Kconfig

+0 −3
Original line number Diff line number Diff line
@@ -14,9 +14,6 @@ config HYPERV 
config HYPERV_TIMER

	def_bool HYPERV



config HYPERV_TSCPAGE

       def_bool HYPERV && X86_64



config HYPERV_UTILS

	tristate "Microsoft Hyper-V Utilities driver"

	depends on HYPERV && CONNECTOR && NLS

include/clocksource/hyperv_timer.h

+3 −5
Original line number Diff line number Diff line
@@ -28,12 +28,10 @@ extern void hv_stimer_cleanup(unsigned int cpu); 
extern void hv_stimer_global_cleanup(void);

extern void hv_stimer0_isr(void);



#if IS_ENABLED(CONFIG_HYPERV)

#ifdef CONFIG_HYPERV_TIMER

extern struct clocksource *hyperv_cs;

extern void hv_init_clocksource(void);

#endif /* CONFIG_HYPERV */



#ifdef CONFIG_HYPERV_TSCPAGE

extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);



static inline notrace u64
@@ -91,7 +89,7 @@ hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg) 
	return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);

}



#else /* CONFIG_HYPERV_TSC_PAGE */

#else /* CONFIG_HYPERV_TIMER */

static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)

{

	return NULL;
@@ -102,6 +100,6 @@ static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, 
{

	return U64_MAX;

}

#endif /* CONFIG_HYPERV_TSCPAGE */

#endif /* CONFIG_HYPERV_TIMER */



#endif