The branch stable/12 has been updated by kib: URL: https://cgit.FreeBSD.org/src/commit/?id=249f2478e38224df653878bc58ab549f1b7c0465
commit 249f2478e38224df653878bc58ab549f1b7c0465 Author: Adam Fenn <[email protected]> AuthorDate: 2021-08-07 20:01:46 +0000 Commit: Konstantin Belousov <[email protected]> CommitDate: 2021-10-12 16:01:26 +0000 pvclock: Add 'struct pvclock' API Consolidate more hypervisor-agnostic functionality behind a new 'struct pvclock' API. This should also make it easier to subsequently add hypervisor-agnostic vDSO timekeeping support. Also, perform some clean-up: - Remove 'pvclock_get_last_cycles()'; do not allow external access to 'pvclock_last_systime' since this is not necessary. - Consolidate/simplify wall and system time reading codepaths. - Ensure correct ordering within wall and system time reading codepaths via 'atomic(9)' and 'rdtsc_ordered()' rather than via 'rmb()'. - Remove some extra newlines. Sponsored by: Juniper Networks, Inc. Sponsored by: Klara, Inc. Reviewed by: kib Differential Revision: https://reviews.freebsd.org/D31418 (cherry picked from commit 0b3382b863f3195d88b99f94d5af7fe4a7b9726a) --- sys/x86/include/pvclock.h | 27 ++++++- sys/x86/x86/pvclock.c | 194 ++++++++++++++++++++++++++++++++-------------- 2 files changed, 160 insertions(+), 61 deletions(-) diff --git a/sys/x86/include/pvclock.h b/sys/x86/include/pvclock.h index 402ffed810ca..399017039dd0 100644 --- a/sys/x86/include/pvclock.h +++ b/sys/x86/include/pvclock.h @@ -29,6 +29,9 @@ #ifndef X86_PVCLOCK #define X86_PVCLOCK +#include <sys/types.h> +#include <sys/timetc.h> + struct pvclock_vcpu_time_info { uint32_t version; uint32_t pad0; @@ -43,17 +46,39 @@ struct pvclock_vcpu_time_info { #define PVCLOCK_FLAG_TSC_STABLE 0x01 #define PVCLOCK_FLAG_GUEST_PASUED 0x02 +typedef struct pvclock_wall_clock *pvclock_get_wallclock_t(void *arg); + struct pvclock_wall_clock { uint32_t version; uint32_t sec; uint32_t nsec; }; +struct pvclock { + /* Public; initialized by the caller of 'pvclock_init()': */ + pvclock_get_wallclock_t *get_wallclock; + void *get_wallclock_arg; + struct pvclock_vcpu_time_info *timeinfos; + bool stable_flag_supported; + + /* Private; initialized by the 'pvclock' API: */ + struct timecounter tc; +}; + +/* + * NOTE: 'pvclock_get_timecount()' and 'pvclock_get_wallclock()' are purely + * transitional; they should be removed after 'dev/xen/timer/timer.c' has been + * migrated to the 'struct pvclock' API. + */ void pvclock_resume(void); -uint64_t pvclock_get_last_cycles(void); uint64_t pvclock_tsc_freq(struct pvclock_vcpu_time_info *ti); uint64_t pvclock_get_timecount(struct pvclock_vcpu_time_info *ti); void pvclock_get_wallclock(struct pvclock_wall_clock *wc, struct timespec *ts); +void pvclock_init(struct pvclock *pvc, device_t dev, + const char *tc_name, int tc_quality, u_int tc_flags); +void pvclock_gettime(struct pvclock *pvc, struct timespec *ts); +int pvclock_destroy(struct pvclock *pvc); + #endif diff --git a/sys/x86/x86/pvclock.c b/sys/x86/x86/pvclock.c index c1e6f83b33bf..e0ad65d906b8 100644 --- a/sys/x86/x86/pvclock.c +++ b/sys/x86/x86/pvclock.c @@ -31,31 +31,34 @@ __FBSDID("$FreeBSD$"); #include <sys/param.h> #include <sys/systm.h> +#include <sys/clock.h> +#include <sys/limits.h> #include <sys/proc.h> -#include <machine/cpufunc.h> -#include <machine/cpu.h> #include <machine/atomic.h> +#include <machine/md_var.h> #include <machine/pvclock.h> /* - * Last time; this guarantees a monotonically increasing clock for when - * a stable TSC is not provided. + * Last system time. This is used to guarantee a monotonically non-decreasing + * clock for the kernel codepath and approximate the same for the vDSO codepath. + * In theory, this should be unnecessary absent hypervisor bug(s) and/or what + * should be rare cases where TSC jitter may still be visible despite the + * hypervisor's best efforts. */ -static volatile uint64_t pvclock_last_cycles; +static volatile uint64_t pvclock_last_systime; + +static uint64_t pvclock_getsystime(struct pvclock *pvc); +static void pvclock_read_time_info( + struct pvclock_vcpu_time_info *ti, uint64_t *ns, uint8_t *flags); +static void pvclock_read_wall_clock(struct pvclock_wall_clock *wc, + struct timespec *ts); +static u_int pvclock_tc_get_timecount(struct timecounter *tc); void pvclock_resume(void) { - - atomic_store_rel_64(&pvclock_last_cycles, 0); -} - -uint64_t -pvclock_get_last_cycles(void) -{ - - return (atomic_load_acq_64(&pvclock_last_cycles)); + atomic_store_rel_64(&pvclock_last_systime, 0); } uint64_t @@ -64,12 +67,10 @@ pvclock_tsc_freq(struct pvclock_vcpu_time_info *ti) uint64_t freq; freq = (1000000000ULL << 32) / ti->tsc_to_system_mul; - if (ti->tsc_shift < 0) freq <<= -ti->tsc_shift; else freq >>= ti->tsc_shift; - return (freq); } @@ -86,7 +87,6 @@ pvclock_scale_delta(uint64_t delta, uint32_t mul_frac, int shift) delta >>= -shift; else delta <<= shift; - #if defined(__i386__) { uint32_t tmp1, tmp2; @@ -122,82 +122,156 @@ pvclock_scale_delta(uint64_t delta, uint32_t mul_frac, int shift) #else #error "pvclock: unsupported x86 architecture?" #endif - return (product); } -static uint64_t -pvclock_get_nsec_offset(struct pvclock_vcpu_time_info *ti) -{ - uint64_t delta; - - delta = rdtsc() - ti->tsc_timestamp; - - return (pvclock_scale_delta(delta, ti->tsc_to_system_mul, - ti->tsc_shift)); -} - static void pvclock_read_time_info(struct pvclock_vcpu_time_info *ti, - uint64_t *cycles, uint8_t *flags) + uint64_t *ns, uint8_t *flags) { + uint64_t delta; uint32_t version; do { - version = ti->version; - rmb(); - *cycles = ti->system_time + pvclock_get_nsec_offset(ti); + version = atomic_load_acq_32(&ti->version); + delta = rdtsc_ordered() - ti->tsc_timestamp; + *ns = ti->system_time + pvclock_scale_delta(delta, + ti->tsc_to_system_mul, ti->tsc_shift); *flags = ti->flags; - rmb(); + atomic_thread_fence_acq(); } while ((ti->version & 1) != 0 || ti->version != version); } static void -pvclock_read_wall_clock(struct pvclock_wall_clock *wc, uint32_t *sec, - uint32_t *nsec) +pvclock_read_wall_clock(struct pvclock_wall_clock *wc, struct timespec *ts) { uint32_t version; do { - version = wc->version; - rmb(); - *sec = wc->sec; - *nsec = wc->nsec; - rmb(); + version = atomic_load_acq_32(&wc->version); + ts->tv_sec = wc->sec; + ts->tv_nsec = wc->nsec; + atomic_thread_fence_acq(); } while ((wc->version & 1) != 0 || wc->version != version); } +static uint64_t +pvclock_getsystime(struct pvclock *pvc) +{ + uint64_t now, last, ret; + uint8_t flags; + + critical_enter(); + pvclock_read_time_info(&pvc->timeinfos[curcpu], &now, &flags); + ret = now; + if ((flags & PVCLOCK_FLAG_TSC_STABLE) == 0) { + last = atomic_load_acq_64(&pvclock_last_systime); + do { + if (last > now) { + ret = last; + break; + } + } while (!atomic_fcmpset_rel_64(&pvclock_last_systime, &last, + now)); + } + critical_exit(); + return (ret); +} + +/* + * NOTE: Transitional-only; this should be removed after 'dev/xen/timer/timer.c' + * has been migrated to the 'struct pvclock' API. + */ uint64_t pvclock_get_timecount(struct pvclock_vcpu_time_info *ti) { - uint64_t now, last; + uint64_t now, last, ret; uint8_t flags; pvclock_read_time_info(ti, &now, &flags); + ret = now; + if ((flags & PVCLOCK_FLAG_TSC_STABLE) == 0) { + last = atomic_load_acq_64(&pvclock_last_systime); + do { + if (last > now) { + ret = last; + break; + } + } while (!atomic_fcmpset_rel_64(&pvclock_last_systime, &last, + now)); + } + return (ret); +} - if (flags & PVCLOCK_FLAG_TSC_STABLE) - return (now); +/* + * NOTE: Transitional-only; this should be removed after 'dev/xen/timer/timer.c' + * has been migrated to the 'struct pvclock' API. + */ +void +pvclock_get_wallclock(struct pvclock_wall_clock *wc, struct timespec *ts) +{ + pvclock_read_wall_clock(wc, ts); +} - /* - * Enforce a monotonically increasing clock time across all VCPUs. - * If our time is too old, use the last time and return. Otherwise, - * try to update the last time. - */ - do { - last = atomic_load_acq_64(&pvclock_last_cycles); - if (last > now) - return (last); - } while (!atomic_cmpset_64(&pvclock_last_cycles, last, now)); +static u_int +pvclock_tc_get_timecount(struct timecounter *tc) +{ + struct pvclock *pvc = tc->tc_priv; - return (now); + return (pvclock_getsystime(pvc) & UINT_MAX); } void -pvclock_get_wallclock(struct pvclock_wall_clock *wc, struct timespec *ts) +pvclock_gettime(struct pvclock *pvc, struct timespec *ts) { - uint32_t sec, nsec; + struct timespec system_ts; + uint64_t system_ns; + + pvclock_read_wall_clock(pvc->get_wallclock(pvc->get_wallclock_arg), ts); + system_ns = pvclock_getsystime(pvc); + system_ts.tv_sec = system_ns / 1000000000ULL; + system_ts.tv_nsec = system_ns % 1000000000ULL; + timespecadd(ts, &system_ts, ts); +} - pvclock_read_wall_clock(wc, &sec, &nsec); - ts->tv_sec = sec; - ts->tv_nsec = nsec; +void +pvclock_init(struct pvclock *pvc, device_t dev, const char *tc_name, + int tc_quality, u_int tc_flags) +{ + KASSERT(((uintptr_t)pvc->timeinfos & PAGE_MASK) == 0, + ("Specified time info page(s) address is not page-aligned.")); + + /* Set up timecounter and timecounter-supporting members: */ + pvc->tc.tc_get_timecount = pvclock_tc_get_timecount; + pvc->tc.tc_poll_pps = NULL; + pvc->tc.tc_counter_mask = ~0U; + pvc->tc.tc_frequency = 1000000000ULL; + pvc->tc.tc_name = tc_name; + pvc->tc.tc_quality = tc_quality; + pvc->tc.tc_flags = tc_flags; + pvc->tc.tc_priv = pvc; + pvc->tc.tc_fill_vdso_timehands = NULL; +#ifdef COMPAT_FREEBSD32 + pvc->tc.tc_fill_vdso_timehands32 = NULL; +#endif + + /* Register timecounter: */ + tc_init(&pvc->tc); + + /* + * Register wallclock: + * The RTC registration API expects a resolution in microseconds; + * pvclock's 1ns resolution is rounded up to 1us. + */ + clock_register(dev, 1); +} + +int +pvclock_destroy(struct pvclock *pvc) +{ + /* + * Not currently possible since there is no teardown counterpart of + * 'tc_init()'. + */ + return (EBUSY); }
