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clocksource/drivers/hyperv: Add Hyper-V specific sched clock function

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Hyper-V guests use the default native_sched_clock() in
pv_ops.time.sched_clock on x86. But native_sched_clock() directly uses the
raw TSC value, which can be discontinuous in a Hyper-V VM.
    
Add the generic hv_setup_sched_clock() to set the sched clock function
appropriately. On x86, this sets pv_ops.time.sched_clock to read the
Hyper-V reference TSC value that is scaled and adjusted to be continuous.
    
Also move the Hyper-V reference TSC initialization much earlier in the boot
process so no discontinuity is observed when pv_ops.time.sched_clock
calculates its offset.

[ tglx: Folded build fix ]

Signed-off-by: Tianyu Lan <Tianyu.Lan@microsoft.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lkml.kernel.org/r/20190814123216.32245-3-Tianyu.Lan@microsoft.com
This commit is contained in:
Tianyu Lan
2019-08-14 20:32:16 +08:00
committed by Thomas Gleixner
parent adb87ff4f9
commit bd00cd52d5
4 changed files with 21 additions and 12 deletions
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22
drivers/clocksource/hyperv_timer.c
View File

@@ -22,6 +22,7 @@
#include <asm/mshyperv.h>
static struct clock_event_device __percpu *hv_clock_event;
static u64 hv_sched_clock_offset __ro_after_init;
/*
* If false, we're using the old mechanism for stimer0 interrupts
@@ -222,7 +223,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);
static u64 notrace read_hv_sched_clock_tsc(void)
static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
{
u64 current_tick = hv_read_tsc_page(&tsc_pg);
@@ -232,9 +233,9 @@ static u64 notrace read_hv_sched_clock_tsc(void)
return current_tick;
}
static u64 read_hv_clock_tsc(struct clocksource *arg)
static u64 read_hv_sched_clock_tsc(void)
{
return read_hv_sched_clock_tsc();
return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
}
static struct clocksource hyperv_cs_tsc = {
@@ -246,7 +247,7 @@ static struct clocksource hyperv_cs_tsc = {
};
#endif
static u64 notrace read_hv_sched_clock_msr(void)
static u64 notrace read_hv_clock_msr(struct clocksource *arg)
{
u64 current_tick;
/*
@@ -258,9 +259,9 @@ static u64 notrace read_hv_sched_clock_msr(void)
return current_tick;
}
static u64 read_hv_clock_msr(struct clocksource *arg)
static u64 read_hv_sched_clock_msr(void)
{
return read_hv_sched_clock_msr();
return read_hv_clock_msr(NULL) - hv_sched_clock_offset;
}
static struct clocksource hyperv_cs_msr = {
@@ -298,8 +299,9 @@ static bool __init hv_init_tsc_clocksource(void)
hv_set_clocksource_vdso(hyperv_cs_tsc);
clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
sched_clock_register(read_hv_sched_clock_tsc, 64, HV_CLOCK_HZ);
hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
hv_setup_sched_clock(read_hv_sched_clock_tsc);
return true;
}
#else
@@ -329,7 +331,7 @@ void __init hv_init_clocksource(void)
hyperv_cs = &hyperv_cs_msr;
clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
/* sched_clock_register is needed on ARM64 but is a no-op on x86 */
sched_clock_register(read_hv_sched_clock_msr, 64, HV_CLOCK_HZ);
hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
hv_setup_sched_clock(read_hv_sched_clock_msr);
}
EXPORT_SYMBOL_GPL(hv_init_clocksource);