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 static __always_inline 68 u64 __pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, bool dowd) 69 { 70 unsigned version; 71 u64 ret; 72 u64 last; 73 u8 flags; 74 75 do { 76 version = pvclock_read_begin(src); 77 ret = __pvclock_read_cycles(src, rdtsc_ordered()); 78 flags = src->flags; 79 } while (pvclock_read_retry(src, version)); 80 81 if (dowd && unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { 82 src->flags &= ~PVCLOCK_GUEST_STOPPED; 83 pvclock_touch_watchdogs(); 84 } 85 86 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && 87 (flags & PVCLOCK_TSC_STABLE_BIT)) 88 return ret; 89 90 /* 91 * Assumption here is that last_value, a global accumulator, always goes 92 * forward. If we are less than that, we should not be much smaller. 93 * We assume there is an error margin we're inside, and then the correction 94 * does not sacrifice accuracy. 95 * 96 * For reads: global may have changed between test and return, 97 * but this means someone else updated poked the clock at a later time. 98 * We just need to make sure we are not seeing a backwards event. 99 * 100 * For updates: last_value = ret is not enough, since two vcpus could be 101 * updating at the same time, and one of them could be slightly behind, 102 * making the assumption that last_value always go forward fail to hold. 103 */ 104 last = arch_atomic64_read(&last_value); 105 do { 106 if (ret <= last) 107 return last; 108 } while (!arch_atomic64_try_cmpxchg(&last_value, &last, ret)); 109 110 return ret; 111 } 112 113 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) 114 { 115 return __pvclock_clocksource_read(src, true); 116 } 117 118 noinstr u64 pvclock_clocksource_read_nowd(struct pvclock_vcpu_time_info *src) 119 { 120 return __pvclock_clocksource_read(src, false); 121 } 122 123 void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, 124 struct pvclock_vcpu_time_info *vcpu_time, 125 struct timespec64 *ts) 126 { 127 u32 version; 128 u64 delta; 129 struct timespec64 now; 130 131 /* get wallclock at system boot */ 132 do { 133 version = wall_clock->version; 134 rmb(); /* fetch version before time */ 135 /* 136 * Note: wall_clock->sec is a u32 value, so it can 137 * only store dates between 1970 and 2106. To allow 138 * times beyond that, we need to create a new hypercall 139 * interface with an extended pvclock_wall_clock structure 140 * like ARM has. 141 */ 142 now.tv_sec = wall_clock->sec; 143 now.tv_nsec = wall_clock->nsec; 144 rmb(); /* fetch time before checking version */ 145 } while ((wall_clock->version & 1) || (version != wall_clock->version)); 146 147 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ 148 delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec; 149 150 now.tv_nsec = do_div(delta, NSEC_PER_SEC); 151 now.tv_sec = delta; 152 153 set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec); 154 } 155 156 void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti) 157 { 158 WARN_ON(vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)); 159 pvti_cpu0_va = pvti; 160 } 161 162 struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void) 163 { 164 return pvti_cpu0_va; 165 } 166 EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va); 167