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/memblock.h> 24 #include <linux/nmi.h> 25 26 #include <asm/fixmap.h> 27 #include <asm/pvclock.h> 28 #include <asm/vgtod.h> 29 30 static u8 valid_flags __read_mostly = 0; 31 static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly; 32 33 void pvclock_set_flags(u8 flags) 34 { 35 valid_flags = flags; 36 } 37 38 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) 39 { 40 u64 pv_tsc_khz = 1000000ULL << 32; 41 42 do_div(pv_tsc_khz, src->tsc_to_system_mul); 43 if (src->tsc_shift < 0) 44 pv_tsc_khz <<= -src->tsc_shift; 45 else 46 pv_tsc_khz >>= src->tsc_shift; 47 return pv_tsc_khz; 48 } 49 50 void pvclock_touch_watchdogs(void) 51 { 52 touch_softlockup_watchdog_sync(); 53 clocksource_touch_watchdog(); 54 rcu_cpu_stall_reset(); 55 reset_hung_task_detector(); 56 } 57 58 static atomic64_t last_value = ATOMIC64_INIT(0); 59 60 void pvclock_resume(void) 61 { 62 atomic64_set(&last_value, 0); 63 } 64 65 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) 66 { 67 unsigned version; 68 u8 flags; 69 70 do { 71 version = pvclock_read_begin(src); 72 flags = src->flags; 73 } while (pvclock_read_retry(src, version)); 74 75 return flags & valid_flags; 76 } 77 78 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) 79 { 80 unsigned version; 81 u64 ret; 82 u64 last; 83 u8 flags; 84 85 do { 86 version = pvclock_read_begin(src); 87 ret = __pvclock_read_cycles(src, rdtsc_ordered()); 88 flags = src->flags; 89 } while (pvclock_read_retry(src, version)); 90 91 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { 92 src->flags &= ~PVCLOCK_GUEST_STOPPED; 93 pvclock_touch_watchdogs(); 94 } 95 96 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && 97 (flags & PVCLOCK_TSC_STABLE_BIT)) 98 return ret; 99 100 /* 101 * Assumption here is that last_value, a global accumulator, always goes 102 * forward. If we are less than that, we should not be much smaller. 103 * We assume there is an error marging we're inside, and then the correction 104 * does not sacrifice accuracy. 105 * 106 * For reads: global may have changed between test and return, 107 * but this means someone else updated poked the clock at a later time. 108 * We just need to make sure we are not seeing a backwards event. 109 * 110 * For updates: last_value = ret is not enough, since two vcpus could be 111 * updating at the same time, and one of them could be slightly behind, 112 * making the assumption that last_value always go forward fail to hold. 113 */ 114 last = atomic64_read(&last_value); 115 do { 116 if (ret < last) 117 return last; 118 last = atomic64_cmpxchg(&last_value, last, ret); 119 } while (unlikely(last != ret)); 120 121 return ret; 122 } 123 124 void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, 125 struct pvclock_vcpu_time_info *vcpu_time, 126 struct timespec64 *ts) 127 { 128 u32 version; 129 u64 delta; 130 struct timespec64 now; 131 132 /* get wallclock at system boot */ 133 do { 134 version = wall_clock->version; 135 rmb(); /* fetch version before time */ 136 /* 137 * Note: wall_clock->sec is a u32 value, so it can 138 * only store dates between 1970 and 2106. To allow 139 * times beyond that, we need to create a new hypercall 140 * interface with an extended pvclock_wall_clock structure 141 * like ARM has. 142 */ 143 now.tv_sec = wall_clock->sec; 144 now.tv_nsec = wall_clock->nsec; 145 rmb(); /* fetch time before checking version */ 146 } while ((wall_clock->version & 1) || (version != wall_clock->version)); 147 148 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ 149 delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec; 150 151 now.tv_nsec = do_div(delta, NSEC_PER_SEC); 152 now.tv_sec = delta; 153 154 set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec); 155 } 156 157 void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti) 158 { 159 WARN_ON(vclock_was_used(VCLOCK_PVCLOCK)); 160 pvti_cpu0_va = pvti; 161 } 162 163 struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void) 164 { 165 return pvti_cpu0_va; 166 } 167 EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va); 168