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clocksource: hyper-v: Provide noinstr sched_clock()

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With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by making the Hyper-V TSC and MSR sched_clock
implementations noinstr.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Co-developed-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com>  # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.843039089@infradead.org
This commit is contained in:
Peter Zijlstra 2023-05-19 12:21:08 +02:00
parent 9397fa2ea3
commit e39acc37db
2 changed files with 23 additions and 14 deletions
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5
arch/x86/include/asm/mshyperv.h
View File

@ -257,6 +257,11 @@ void hv_set_register(unsigned int reg, u64 value);
u64 hv_get_non_nested_register(unsigned int reg);
void hv_set_non_nested_register(unsigned int reg, u64 value);
static __always_inline u64 hv_raw_get_register(unsigned int reg)
{
return __rdmsr(reg);
}
#else /* CONFIG_HYPERV */
static inline void hyperv_init(void) {}
static inline void hyperv_setup_mmu_ops(void) {}

32
drivers/clocksource/hyperv_timer.c
View File

@ -365,6 +365,20 @@ void hv_stimer_global_cleanup(void)
}
EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
static __always_inline u64 read_hv_clock_msr(void)
{
/*
* Read the partition counter to get the current tick count. This count
* is set to 0 when the partition is created and is incremented in 100
* nanosecond units.
*
* Use hv_raw_get_register() because this function is used from
* noinstr. Notable; while HV_REGISTER_TIME_REF_COUNT is a synthetic
* register it doesn't need the GHCB path.
*/
return hv_raw_get_register(HV_REGISTER_TIME_REF_COUNT);
}
/*
* Code and definitions for the Hyper-V clocksources. Two
* clocksources are defined: one that reads the Hyper-V defined MSR, and
@ -393,7 +407,7 @@ struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);
static notrace u64 read_hv_clock_tsc(void)
static __always_inline u64 read_hv_clock_tsc(void)
{
u64 cur_tsc, time;
@ -404,7 +418,7 @@ static notrace u64 read_hv_clock_tsc(void)
* to the MSR in case the TSC page indicates unavailability.
*/
if (!hv_read_tsc_page_tsc(tsc_page, &cur_tsc, &time))
time = hv_get_register(HV_REGISTER_TIME_REF_COUNT);
time = read_hv_clock_msr();
return time;
}
@ -414,7 +428,7 @@ static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
return read_hv_clock_tsc();
}
static u64 notrace read_hv_sched_clock_tsc(void)
static u64 noinstr read_hv_sched_clock_tsc(void)
{
return (read_hv_clock_tsc() - hv_sched_clock_offset) *
(NSEC_PER_SEC / HV_CLOCK_HZ);
@ -466,22 +480,12 @@ static struct clocksource hyperv_cs_tsc = {
#endif
};
static u64 notrace read_hv_clock_msr(void)
{
/*
* Read the partition counter to get the current tick count. This count
* is set to 0 when the partition is created and is incremented in
* 100 nanosecond units.
*/
return hv_get_register(HV_REGISTER_TIME_REF_COUNT);
}
static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
{
return read_hv_clock_msr();
}
static u64 notrace read_hv_sched_clock_msr(void)
static u64 noinstr read_hv_sched_clock_msr(void)
{
return (read_hv_clock_msr() - hv_sched_clock_offset) *
(NSEC_PER_SEC / HV_CLOCK_HZ);