| 1 | /* paravirtual clock -- common code used by kvm/xen |
| 2 | |
| 3 | This program is free software; you can redistribute it and/or modify |
| 4 | it under the terms of the GNU General Public License as published by |
| 5 | the Free Software Foundation; either version 2 of the License, or |
| 6 | (at your option) any later version. |
| 7 | |
| 8 | This program is distributed in the hope that it will be useful, |
| 9 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 10 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 11 | GNU General Public License for more details. |
| 12 | |
| 13 | You should have received a copy of the GNU General Public License |
| 14 | along with this program; if not, write to the Free Software |
| 15 | Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| 16 | */ |
| 17 | |
| 18 | #include <linux/kernel.h> |
| 19 | #include <linux/percpu.h> |
| 20 | #include <linux/notifier.h> |
| 21 | #include <linux/sched.h> |
| 22 | #include <linux/gfp.h> |
| 23 | #include <linux/bootmem.h> |
| 24 | #include <asm/fixmap.h> |
| 25 | #include <asm/pvclock.h> |
| 26 | |
| 27 | static u8 valid_flags __read_mostly = 0; |
| 28 | |
| 29 | void pvclock_set_flags(u8 flags) |
| 30 | { |
| 31 | valid_flags = flags; |
| 32 | } |
| 33 | |
| 34 | unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) |
| 35 | { |
| 36 | u64 pv_tsc_khz = 1000000ULL << 32; |
| 37 | |
| 38 | do_div(pv_tsc_khz, src->tsc_to_system_mul); |
| 39 | if (src->tsc_shift < 0) |
| 40 | pv_tsc_khz <<= -src->tsc_shift; |
| 41 | else |
| 42 | pv_tsc_khz >>= src->tsc_shift; |
| 43 | return pv_tsc_khz; |
| 44 | } |
| 45 | |
| 46 | void pvclock_touch_watchdogs(void) |
| 47 | { |
| 48 | touch_softlockup_watchdog_sync(); |
| 49 | clocksource_touch_watchdog(); |
| 50 | rcu_cpu_stall_reset(); |
| 51 | reset_hung_task_detector(); |
| 52 | } |
| 53 | |
| 54 | static atomic64_t last_value = ATOMIC64_INIT(0); |
| 55 | |
| 56 | void pvclock_resume(void) |
| 57 | { |
| 58 | atomic64_set(&last_value, 0); |
| 59 | } |
| 60 | |
| 61 | u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) |
| 62 | { |
| 63 | unsigned version; |
| 64 | u8 flags; |
| 65 | |
| 66 | do { |
| 67 | version = pvclock_read_begin(src); |
| 68 | flags = src->flags; |
| 69 | } while (pvclock_read_retry(src, version)); |
| 70 | |
| 71 | return flags & valid_flags; |
| 72 | } |
| 73 | |
| 74 | cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
| 75 | { |
| 76 | unsigned version; |
| 77 | cycle_t ret; |
| 78 | u64 last; |
| 79 | u8 flags; |
| 80 | |
| 81 | do { |
| 82 | version = pvclock_read_begin(src); |
| 83 | ret = __pvclock_read_cycles(src); |
| 84 | flags = src->flags; |
| 85 | } while (pvclock_read_retry(src, version)); |
| 86 | |
| 87 | if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { |
| 88 | src->flags &= ~PVCLOCK_GUEST_STOPPED; |
| 89 | pvclock_touch_watchdogs(); |
| 90 | } |
| 91 | |
| 92 | if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && |
| 93 | (flags & PVCLOCK_TSC_STABLE_BIT)) |
| 94 | return ret; |
| 95 | |
| 96 | /* |
| 97 | * Assumption here is that last_value, a global accumulator, always goes |
| 98 | * forward. If we are less than that, we should not be much smaller. |
| 99 | * We assume there is an error marging we're inside, and then the correction |
| 100 | * does not sacrifice accuracy. |
| 101 | * |
| 102 | * For reads: global may have changed between test and return, |
| 103 | * but this means someone else updated poked the clock at a later time. |
| 104 | * We just need to make sure we are not seeing a backwards event. |
| 105 | * |
| 106 | * For updates: last_value = ret is not enough, since two vcpus could be |
| 107 | * updating at the same time, and one of them could be slightly behind, |
| 108 | * making the assumption that last_value always go forward fail to hold. |
| 109 | */ |
| 110 | last = atomic64_read(&last_value); |
| 111 | do { |
| 112 | if (ret < last) |
| 113 | return last; |
| 114 | last = atomic64_cmpxchg(&last_value, last, ret); |
| 115 | } while (unlikely(last != ret)); |
| 116 | |
| 117 | return ret; |
| 118 | } |
| 119 | |
| 120 | void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, |
| 121 | struct pvclock_vcpu_time_info *vcpu_time, |
| 122 | struct timespec *ts) |
| 123 | { |
| 124 | u32 version; |
| 125 | u64 delta; |
| 126 | struct timespec now; |
| 127 | |
| 128 | /* get wallclock at system boot */ |
| 129 | do { |
| 130 | version = wall_clock->version; |
| 131 | rmb(); /* fetch version before time */ |
| 132 | now.tv_sec = wall_clock->sec; |
| 133 | now.tv_nsec = wall_clock->nsec; |
| 134 | rmb(); /* fetch time before checking version */ |
| 135 | } while ((wall_clock->version & 1) || (version != wall_clock->version)); |
| 136 | |
| 137 | delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ |
| 138 | delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; |
| 139 | |
| 140 | now.tv_nsec = do_div(delta, NSEC_PER_SEC); |
| 141 | now.tv_sec = delta; |
| 142 | |
| 143 | set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); |
| 144 | } |