diff options
Diffstat (limited to 'include/clocksource/hyperv_timer.h')
| -rw-r--r-- | include/clocksource/hyperv_timer.h | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h index 0cd73f7bc992..a821deb8ecb2 100644 --- a/include/clocksource/hyperv_timer.h +++ b/include/clocksource/hyperv_timer.h @@ -13,6 +13,10 @@ #ifndef __CLKSOURCE_HYPERV_TIMER_H #define __CLKSOURCE_HYPERV_TIMER_H +#include <linux/clocksource.h> +#include <linux/math64.h> +#include <asm/mshyperv.h> + #define HV_MAX_MAX_DELTA_TICKS 0xffffffff #define HV_MIN_DELTA_TICKS 1 @@ -24,4 +28,80 @@ 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) +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 +hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, u64 *cur_tsc) +{ + u64 scale, offset; + u32 sequence; + + /* + * The protocol for reading Hyper-V TSC page is specified in Hypervisor + * Top-Level Functional Specification ver. 3.0 and above. To get the + * reference time we must do the following: + * - READ ReferenceTscSequence + * A special '0' value indicates the time source is unreliable and we + * need to use something else. The currently published specification + * versions (up to 4.0b) contain a mistake and wrongly claim '-1' + * instead of '0' as the special value, see commit c35b82ef0294. + * - ReferenceTime = + * ((RDTSC() * ReferenceTscScale) >> 64) + ReferenceTscOffset + * - READ ReferenceTscSequence again. In case its value has changed + * since our first reading we need to discard ReferenceTime and repeat + * the whole sequence as the hypervisor was updating the page in + * between. + */ + do { + sequence = READ_ONCE(tsc_pg->tsc_sequence); + if (!sequence) + return U64_MAX; + /* + * Make sure we read sequence before we read other values from + * TSC page. + */ + smp_rmb(); + + scale = READ_ONCE(tsc_pg->tsc_scale); + offset = READ_ONCE(tsc_pg->tsc_offset); + *cur_tsc = hv_get_raw_timer(); + + /* + * Make sure we read sequence after we read all other values + * from TSC page. + */ + smp_rmb(); + + } while (READ_ONCE(tsc_pg->tsc_sequence) != sequence); + + return mul_u64_u64_shr(*cur_tsc, scale, 64) + offset; +} + +static inline notrace u64 +hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg) +{ + u64 cur_tsc; + + return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc); +} + +#else /* CONFIG_HYPERV_TSC_PAGE */ +static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void) +{ + return NULL; +} + +static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg, + u64 *cur_tsc) +{ + return U64_MAX; +} +#endif /* CONFIG_HYPERV_TSCPAGE */ + #endif |