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: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lkml.kernel.org/r/20190822083630.17059-1-vkuznets@redhat.com

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

@@ -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

@@ -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

@@ -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

@@ -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