1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2014 Bryan Venteicher <bryanv@FreeBSD.org> 5 * Copyright (c) 2021 Mathieu Chouquet-Stringer 6 * Copyright (c) 2021 Juniper Networks, Inc. 7 * Copyright (c) 2021 Klara, Inc. 8 * 9 * Redistribution and use in source and binary forms, with or without 10 * modification, are permitted provided that the following conditions 11 * are met: 12 * 1. Redistributions of source code must retain the above copyright 13 * notice, this list of conditions and the following disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31 /* 32 * Linux KVM paravirtual clock support 33 * 34 * References: 35 * - [1] https://www.kernel.org/doc/html/latest/virt/kvm/cpuid.html 36 * - [2] https://www.kernel.org/doc/html/latest/virt/kvm/msr.html 37 */ 38 39 #include <sys/cdefs.h> 40 #include <sys/param.h> 41 #include <sys/bus.h> 42 #include <sys/domainset.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/module.h> 46 #include <sys/smp.h> 47 #include <sys/sysctl.h> 48 49 #include <vm/vm.h> 50 #include <vm/pmap.h> 51 #include <vm/vm_extern.h> 52 53 #include <machine/pvclock.h> 54 #include <x86/kvm.h> 55 56 #include "clock_if.h" 57 58 #define KVM_CLOCK_DEVNAME "kvmclock" 59 /* 60 * Note: Chosen to be (1) above HPET's value (always 950), (2) above the TSC's 61 * default value of 800, and (3) below the TSC's value when it supports the 62 * "Invariant TSC" feature and is believed to be synchronized across all CPUs. 63 */ 64 #define KVM_CLOCK_TC_QUALITY 975 65 66 struct kvm_clock_softc { 67 struct pvclock pvc; 68 struct pvclock_wall_clock wc; 69 struct pvclock_vcpu_time_info *timeinfos; 70 u_int msr_tc; 71 u_int msr_wc; 72 #ifndef EARLY_AP_STARTUP 73 int firstcpu; 74 #endif 75 }; 76 77 static struct pvclock_wall_clock *kvm_clock_get_wallclock(void *arg); 78 static void kvm_clock_system_time_enable(struct kvm_clock_softc *sc, 79 const cpuset_t *cpus); 80 static void kvm_clock_system_time_enable_pcpu(void *arg); 81 static void kvm_clock_setup_sysctl(device_t); 82 83 static struct pvclock_wall_clock * 84 kvm_clock_get_wallclock(void *arg) 85 { 86 struct kvm_clock_softc *sc = arg; 87 88 wrmsr(sc->msr_wc, vtophys(&sc->wc)); 89 return (&sc->wc); 90 } 91 92 static void 93 kvm_clock_system_time_enable(struct kvm_clock_softc *sc, const cpuset_t *cpus) 94 { 95 smp_rendezvous_cpus(*cpus, NULL, kvm_clock_system_time_enable_pcpu, 96 NULL, sc); 97 } 98 99 static void 100 kvm_clock_system_time_enable_pcpu(void *arg) 101 { 102 struct kvm_clock_softc *sc = arg; 103 104 /* 105 * See [2]; the lsb of this MSR is the system time enable bit. 106 */ 107 wrmsr(sc->msr_tc, vtophys(&(sc->timeinfos)[curcpu]) | 1); 108 } 109 110 #ifndef EARLY_AP_STARTUP 111 static void 112 kvm_clock_init_smp(void *arg __unused) 113 { 114 devclass_t kvm_clock_devclass; 115 cpuset_t cpus; 116 struct kvm_clock_softc *sc; 117 118 kvm_clock_devclass = devclass_find(KVM_CLOCK_DEVNAME); 119 sc = devclass_get_softc(kvm_clock_devclass, 0); 120 if (sc == NULL || mp_ncpus == 1) 121 return; 122 123 /* 124 * Register with the hypervisor on all CPUs except the one that 125 * registered in kvm_clock_attach(). 126 */ 127 cpus = all_cpus; 128 KASSERT(CPU_ISSET(sc->firstcpu, &cpus), 129 ("%s: invalid first CPU %d", __func__, sc->firstcpu)); 130 CPU_CLR(sc->firstcpu, &cpus); 131 kvm_clock_system_time_enable(sc, &cpus); 132 } 133 SYSINIT(kvm_clock, SI_SUB_SMP, SI_ORDER_ANY, kvm_clock_init_smp, NULL); 134 #endif 135 136 static void 137 kvm_clock_identify(driver_t *driver, device_t parent) 138 { 139 u_int regs[4]; 140 141 kvm_cpuid_get_features(regs); 142 if ((regs[0] & 143 (KVM_FEATURE_CLOCKSOURCE2 | KVM_FEATURE_CLOCKSOURCE)) == 0) 144 return; 145 if (device_find_child(parent, KVM_CLOCK_DEVNAME, -1)) 146 return; 147 BUS_ADD_CHILD(parent, 0, KVM_CLOCK_DEVNAME, 0); 148 } 149 150 static int 151 kvm_clock_probe(device_t dev) 152 { 153 device_set_desc(dev, "KVM paravirtual clock"); 154 return (BUS_PROBE_DEFAULT); 155 } 156 157 static int 158 kvm_clock_attach(device_t dev) 159 { 160 u_int regs[4]; 161 struct kvm_clock_softc *sc = device_get_softc(dev); 162 bool stable_flag_supported; 163 164 /* Process KVM "features" CPUID leaf content: */ 165 kvm_cpuid_get_features(regs); 166 if ((regs[0] & KVM_FEATURE_CLOCKSOURCE2) != 0) { 167 sc->msr_tc = KVM_MSR_SYSTEM_TIME_NEW; 168 sc->msr_wc = KVM_MSR_WALL_CLOCK_NEW; 169 } else { 170 KASSERT((regs[0] & KVM_FEATURE_CLOCKSOURCE) != 0, 171 ("Clocksource feature flags disappeared since " 172 "kvm_clock_identify: regs[0] %#0x.", regs[0])); 173 sc->msr_tc = KVM_MSR_SYSTEM_TIME; 174 sc->msr_wc = KVM_MSR_WALL_CLOCK; 175 } 176 stable_flag_supported = 177 (regs[0] & KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) != 0; 178 179 /* Set up 'struct pvclock_vcpu_time_info' page(s): */ 180 sc->timeinfos = kmem_malloc(mp_ncpus * 181 sizeof(struct pvclock_vcpu_time_info), M_WAITOK | M_ZERO); 182 #ifdef EARLY_AP_STARTUP 183 kvm_clock_system_time_enable(sc, &all_cpus); 184 #else 185 sc->firstcpu = curcpu; 186 kvm_clock_system_time_enable_pcpu(sc); 187 #endif 188 189 /* 190 * Init pvclock; register KVM clock wall clock, register KVM clock 191 * timecounter, and set up the requisite infrastructure for vDSO access 192 * to this timecounter. 193 * Regarding 'tc_flags': Since the KVM MSR documentation does not 194 * specifically discuss suspend/resume scenarios, conservatively 195 * leave 'TC_FLAGS_SUSPEND_SAFE' cleared and assume that the system 196 * time must be re-inited in such cases. 197 */ 198 sc->pvc.get_wallclock = kvm_clock_get_wallclock; 199 sc->pvc.get_wallclock_arg = sc; 200 sc->pvc.timeinfos = sc->timeinfos; 201 sc->pvc.stable_flag_supported = stable_flag_supported; 202 pvclock_init(&sc->pvc, dev, KVM_CLOCK_DEVNAME, KVM_CLOCK_TC_QUALITY, 0); 203 kvm_clock_setup_sysctl(dev); 204 return (0); 205 } 206 207 static int 208 kvm_clock_detach(device_t dev) 209 { 210 struct kvm_clock_softc *sc = device_get_softc(dev); 211 212 return (pvclock_destroy(&sc->pvc)); 213 } 214 215 static int 216 kvm_clock_suspend(device_t dev) 217 { 218 return (0); 219 } 220 221 static int 222 kvm_clock_resume(device_t dev) 223 { 224 /* 225 * See note in 'kvm_clock_attach()' regarding 'TC_FLAGS_SUSPEND_SAFE'; 226 * conservatively assume that the system time must be re-inited in 227 * suspend/resume scenarios. 228 */ 229 kvm_clock_system_time_enable(device_get_softc(dev), &all_cpus); 230 pvclock_resume(); 231 inittodr(time_second); 232 return (0); 233 } 234 235 static int 236 kvm_clock_gettime(device_t dev, struct timespec *ts) 237 { 238 struct kvm_clock_softc *sc = device_get_softc(dev); 239 240 pvclock_gettime(&sc->pvc, ts); 241 return (0); 242 } 243 244 static int 245 kvm_clock_settime(device_t dev, struct timespec *ts) 246 { 247 /* 248 * Even though it is not possible to set the KVM clock's wall clock, to 249 * avoid the possibility of periodic benign error messages from 250 * 'settime_task_func()', report success rather than, e.g., 'ENODEV'. 251 */ 252 return (0); 253 } 254 255 static int 256 kvm_clock_tsc_freq_sysctl(SYSCTL_HANDLER_ARGS) 257 { 258 struct kvm_clock_softc *sc = oidp->oid_arg1; 259 uint64_t freq = pvclock_tsc_freq(sc->timeinfos); 260 261 return (sysctl_handle_64(oidp, &freq, 0, req)); 262 } 263 264 static void 265 kvm_clock_setup_sysctl(device_t dev) 266 { 267 struct kvm_clock_softc *sc = device_get_softc(dev); 268 struct sysctl_ctx_list *ctx = device_get_sysctl_ctx(dev); 269 struct sysctl_oid *tree = device_get_sysctl_tree(dev); 270 struct sysctl_oid_list *child = SYSCTL_CHILDREN(tree); 271 272 SYSCTL_ADD_PROC(ctx, child, OID_AUTO, "tsc_freq", 273 CTLTYPE_U64 | CTLFLAG_RD | CTLFLAG_MPSAFE, sc, 0, 274 kvm_clock_tsc_freq_sysctl, "QU", 275 "Time Stamp Counter frequency"); 276 } 277 278 static device_method_t kvm_clock_methods[] = { 279 DEVMETHOD(device_identify, kvm_clock_identify), 280 DEVMETHOD(device_probe, kvm_clock_probe), 281 DEVMETHOD(device_attach, kvm_clock_attach), 282 DEVMETHOD(device_detach, kvm_clock_detach), 283 DEVMETHOD(device_suspend, kvm_clock_suspend), 284 DEVMETHOD(device_resume, kvm_clock_resume), 285 /* clock interface */ 286 DEVMETHOD(clock_gettime, kvm_clock_gettime), 287 DEVMETHOD(clock_settime, kvm_clock_settime), 288 289 DEVMETHOD_END 290 }; 291 292 static driver_t kvm_clock_driver = { 293 KVM_CLOCK_DEVNAME, 294 kvm_clock_methods, 295 sizeof(struct kvm_clock_softc), 296 }; 297 298 DRIVER_MODULE(kvm_clock, nexus, kvm_clock_driver, 0, 0); 299