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Subject[PATCH] x86/hyper-v: enable TSC page clocksource on 32bit
Date
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 (unilizing vDSO in case of TSC page):
MSR based clocksource: 5664 cycles
TSC page clocksource: 131 cycles

Enabling TSC page on 32bits allows us 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>
---
arch/x86/include/asm/vdso/gettimeofday.h | 6 +++---
drivers/clocksource/hyperv_timer.c | 11 -----------
drivers/hv/Kconfig | 3 ---
include/clocksource/hyperv_timer.h | 6 ++----
4 files changed, 5 insertions(+), 21 deletions(-)

diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index ba71a63cdac4..e9ee139cf29e 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/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
@@ -228,7 +228,7 @@ 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);
@@ -251,7 +251,7 @@ 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();
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index ba2c79e6a0ee..b6083faab540 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -212,8 +212,6 @@ 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;

struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
@@ -244,7 +242,6 @@ static struct clocksource hyperv_cs_tsc = {
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
-#endif

static u64 notrace read_hv_sched_clock_msr(void)
{
@@ -271,7 +268,6 @@ 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;
@@ -306,13 +302,6 @@ static bool __init hv_init_tsc_clocksource(void)
sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
return true;
}
-#else
-static bool __init hv_init_tsc_clocksource(void)
-{
- return false;
-}
-#endif
-

void __init hv_init_clocksource(void)
{
diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
index 9a59957922d4..79e5356a737a 100644
--- a/drivers/hv/Kconfig
+++ b/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
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index a821deb8ecb2..f72e4619d0a7 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/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
@@ -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
--
2.20.1
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