1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* paravirtual clock -- common code used by kvm/xen 3 4 */ 5 6 #include <linux/clocksource.h> 7 #include <linux/kernel.h> 8 #include <linux/percpu.h> 9 #include <linux/notifier.h> 10 #include <linux/sched.h> 11 #include <linux/gfp.h> 12 #include <linux/memblock.h> 13 #include <linux/nmi.h> 14 15 #include <asm/fixmap.h> 16 #include <asm/pvclock.h> 17 #include <asm/vgtod.h> 18 19 static u8 valid_flags __read_mostly = 0; 20 static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly; 21 22 void pvclock_set_flags(u8 flags) 23 { 24 valid_flags = flags; 25 } 26 27 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) 28 { 29 u64 pv_tsc_khz = 1000000ULL << 32; 30 31 do_div(pv_tsc_khz, src->tsc_to_system_mul); 32 if (src->tsc_shift < 0) 33 pv_tsc_khz <<= -src->tsc_shift; 34 else 35 pv_tsc_khz >>= src->tsc_shift; 36 return pv_tsc_khz; 37 } 38 39 void pvclock_touch_watchdogs(void) 40 { 41 touch_softlockup_watchdog_sync(); 42 clocksource_touch_watchdog(); 43 rcu_cpu_stall_reset(); 44 reset_hung_task_detector(); 45 } 46 47 static atomic64_t last_value = ATOMIC64_INIT(0); 48 49 void pvclock_resume(void) 50 { 51 atomic64_set(&last_value, 0); 52 } 53 54 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) 55 { 56 unsigned version; 57 u8 flags; 58 59 do { 60 version = pvclock_read_begin(src); 61 flags = src->flags; 62 } while (pvclock_read_retry(src, version)); 63 64 return flags & valid_flags; 65 } 66 67 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) 68 { 69 unsigned version; 70 u64 ret; 71 u64 last; 72 u8 flags; 73 74 do { 75 version = pvclock_read_begin(src); 76 ret = __pvclock_read_cycles(src, rdtsc_ordered()); 77 flags = src->flags; 78 } while (pvclock_read_retry(src, version)); 79 80 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { 81 src->flags &= ~PVCLOCK_GUEST_STOPPED; 82 pvclock_touch_watchdogs(); 83 } 84 85 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && 86 (flags & PVCLOCK_TSC_STABLE_BIT)) 87 return ret; 88 89 /* 90 * Assumption here is that last_value, a global accumulator, always goes 91 * forward. If we are less than that, we should not be much smaller. 92 * We assume there is an error marging we're inside, and then the correction 93 * does not sacrifice accuracy. 94 * 95 * For reads: global may have changed between test and return, 96 * but this means someone else updated poked the clock at a later time. 97 * We just need to make sure we are not seeing a backwards event. 98 * 99 * For updates: last_value = ret is not enough, since two vcpus could be 100 * updating at the same time, and one of them could be slightly behind, 101 * making the assumption that last_value always go forward fail to hold. 102 */ 103 last = atomic64_read(&last_value); 104 do { 105 if (ret < last) 106 return last; 107 last = atomic64_cmpxchg(&last_value, last, ret); 108 } while (unlikely(last != ret)); 109 110 return ret; 111 } 112 113 void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, 114 struct pvclock_vcpu_time_info *vcpu_time, 115 struct timespec64 *ts) 116 { 117 u32 version; 118 u64 delta; 119 struct timespec64 now; 120 121 /* get wallclock at system boot */ 122 do { 123 version = wall_clock->version; 124 rmb(); /* fetch version before time */ 125 /* 126 * Note: wall_clock->sec is a u32 value, so it can 127 * only store dates between 1970 and 2106. To allow 128 * times beyond that, we need to create a new hypercall 129 * interface with an extended pvclock_wall_clock structure 130 * like ARM has. 131 */ 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 * 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_timespec64(ts, now.tv_sec, now.tv_nsec); 144 } 145 146 void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti) 147 { 148 WARN_ON(vclock_was_used(VCLOCK_PVCLOCK)); 149 pvti_cpu0_va = pvti; 150 } 151 152 struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void) 153 { 154 return pvti_cpu0_va; 155 } 156 EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va); 157