1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 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 __FBSDID("$FreeBSD$"); 41 42 #include <sys/param.h> 43 #include <sys/bus.h> 44 #include <sys/domainset.h> 45 #include <sys/kernel.h> 46 #include <sys/malloc.h> 47 #include <sys/module.h> 48 #include <sys/smp.h> 49 #include <sys/sysctl.h> 50 51 #include <vm/vm.h> 52 #include <vm/pmap.h> 53 #include <vm/vm_extern.h> 54 55 #include <machine/pvclock.h> 56 #include <x86/kvm.h> 57 58 #include "clock_if.h" 59 60 #define KVM_CLOCK_DEVNAME "kvmclock" 61 /* 62 * Note: Chosen to be (1) above HPET's value (always 950), (2) above the TSC's 63 * default value of 800, and (3) below the TSC's value when it supports the 64 * "Invariant TSC" feature and is believed to be synchronized across all CPUs. 65 */ 66 #define KVM_CLOCK_TC_QUALITY 975 67 68 struct kvm_clock_softc { 69 struct pvclock pvc; 70 struct pvclock_wall_clock wc; 71 struct pvclock_vcpu_time_info *timeinfos; 72 u_int msr_tc; 73 u_int msr_wc; 74 }; 75 76 static struct pvclock_wall_clock *kvm_clock_get_wallclock(void *arg); 77 static void kvm_clock_system_time_enable(struct kvm_clock_softc *sc); 78 static void kvm_clock_system_time_enable_pcpu(void *arg); 79 static void kvm_clock_setup_sysctl(device_t); 80 81 static struct pvclock_wall_clock * 82 kvm_clock_get_wallclock(void *arg) 83 { 84 struct kvm_clock_softc *sc = arg; 85 86 wrmsr(sc->msr_wc, vtophys(&sc->wc)); 87 return (&sc->wc); 88 } 89 90 static void 91 kvm_clock_system_time_enable(struct kvm_clock_softc *sc) 92 { 93 smp_rendezvous(NULL, kvm_clock_system_time_enable_pcpu, NULL, sc); 94 } 95 96 static void 97 kvm_clock_system_time_enable_pcpu(void *arg) 98 { 99 struct kvm_clock_softc *sc = arg; 100 101 /* 102 * See [2]; the lsb of this MSR is the system time enable bit. 103 */ 104 wrmsr(sc->msr_tc, vtophys(&(sc->timeinfos)[curcpu]) | 1); 105 } 106 107 static void 108 kvm_clock_identify(driver_t *driver, device_t parent) 109 { 110 u_int regs[4]; 111 112 kvm_cpuid_get_features(regs); 113 if ((regs[0] & 114 (KVM_FEATURE_CLOCKSOURCE2 | KVM_FEATURE_CLOCKSOURCE)) == 0) 115 return; 116 if (device_find_child(parent, KVM_CLOCK_DEVNAME, -1)) 117 return; 118 BUS_ADD_CHILD(parent, 0, KVM_CLOCK_DEVNAME, 0); 119 } 120 121 static int 122 kvm_clock_probe(device_t dev) 123 { 124 device_set_desc(dev, "KVM paravirtual clock"); 125 return (BUS_PROBE_DEFAULT); 126 } 127 128 static int 129 kvm_clock_attach(device_t dev) 130 { 131 u_int regs[4]; 132 struct kvm_clock_softc *sc = device_get_softc(dev); 133 bool stable_flag_supported; 134 135 /* Process KVM "features" CPUID leaf content: */ 136 kvm_cpuid_get_features(regs); 137 if ((regs[0] & KVM_FEATURE_CLOCKSOURCE2) != 0) { 138 sc->msr_tc = KVM_MSR_SYSTEM_TIME_NEW; 139 sc->msr_wc = KVM_MSR_WALL_CLOCK_NEW; 140 } else { 141 KASSERT((regs[0] & KVM_FEATURE_CLOCKSOURCE) != 0, 142 ("Clocksource feature flags disappeared since " 143 "kvm_clock_identify: regs[0] %#0x.", regs[0])); 144 sc->msr_tc = KVM_MSR_SYSTEM_TIME; 145 sc->msr_wc = KVM_MSR_WALL_CLOCK; 146 } 147 stable_flag_supported = 148 (regs[0] & KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) != 0; 149 150 /* Set up 'struct pvclock_vcpu_time_info' page(s): */ 151 sc->timeinfos = (struct pvclock_vcpu_time_info *)kmem_malloc(mp_ncpus * 152 sizeof(struct pvclock_vcpu_time_info), M_WAITOK | M_ZERO); 153 kvm_clock_system_time_enable(sc); 154 155 /* 156 * Init pvclock; register KVM clock wall clock, register KVM clock 157 * timecounter, and set up the requisite infrastructure for vDSO access 158 * to this timecounter. 159 * Regarding 'tc_flags': Since the KVM MSR documentation does not 160 * specifically discuss suspend/resume scenarios, conservatively 161 * leave 'TC_FLAGS_SUSPEND_SAFE' cleared and assume that the system 162 * time must be re-inited in such cases. 163 */ 164 sc->pvc.get_wallclock = kvm_clock_get_wallclock; 165 sc->pvc.get_wallclock_arg = sc; 166 sc->pvc.timeinfos = sc->timeinfos; 167 sc->pvc.stable_flag_supported = stable_flag_supported; 168 pvclock_init(&sc->pvc, dev, KVM_CLOCK_DEVNAME, KVM_CLOCK_TC_QUALITY, 0); 169 kvm_clock_setup_sysctl(dev); 170 return (0); 171 } 172 173 static int 174 kvm_clock_detach(device_t dev) 175 { 176 struct kvm_clock_softc *sc = device_get_softc(dev); 177 178 return (pvclock_destroy(&sc->pvc)); 179 } 180 181 static int 182 kvm_clock_suspend(device_t dev) 183 { 184 return (0); 185 } 186 187 static int 188 kvm_clock_resume(device_t dev) 189 { 190 /* 191 * See note in 'kvm_clock_attach()' regarding 'TC_FLAGS_SUSPEND_SAFE'; 192 * conservatively assume that the system time must be re-inited in 193 * suspend/resume scenarios. 194 */ 195 kvm_clock_system_time_enable(device_get_softc(dev)); 196 pvclock_resume(); 197 inittodr(time_second); 198 return (0); 199 } 200 201 static int 202 kvm_clock_gettime(device_t dev, struct timespec *ts) 203 { 204 struct kvm_clock_softc *sc = device_get_softc(dev); 205 206 pvclock_gettime(&sc->pvc, ts); 207 return (0); 208 } 209 210 static int 211 kvm_clock_settime(device_t dev, struct timespec *ts) 212 { 213 /* 214 * Even though it is not possible to set the KVM clock's wall clock, to 215 * avoid the possibility of periodic benign error messages from 216 * 'settime_task_func()', report success rather than, e.g., 'ENODEV'. 217 */ 218 return (0); 219 } 220 221 static int 222 kvm_clock_tsc_freq_sysctl(SYSCTL_HANDLER_ARGS) 223 { 224 struct kvm_clock_softc *sc = oidp->oid_arg1; 225 uint64_t freq = pvclock_tsc_freq(sc->timeinfos); 226 227 return (sysctl_handle_64(oidp, &freq, 0, req)); 228 } 229 230 static void 231 kvm_clock_setup_sysctl(device_t dev) 232 { 233 struct kvm_clock_softc *sc = device_get_softc(dev); 234 struct sysctl_ctx_list *ctx = device_get_sysctl_ctx(dev); 235 struct sysctl_oid *tree = device_get_sysctl_tree(dev); 236 struct sysctl_oid_list *child = SYSCTL_CHILDREN(tree); 237 238 SYSCTL_ADD_PROC(ctx, child, OID_AUTO, "tsc_freq", 239 CTLTYPE_U64 | CTLFLAG_RD | CTLFLAG_MPSAFE, sc, 0, 240 kvm_clock_tsc_freq_sysctl, "QU", 241 "Time Stamp Counter frequency"); 242 } 243 244 static device_method_t kvm_clock_methods[] = { 245 DEVMETHOD(device_identify, kvm_clock_identify), 246 DEVMETHOD(device_probe, kvm_clock_probe), 247 DEVMETHOD(device_attach, kvm_clock_attach), 248 DEVMETHOD(device_detach, kvm_clock_detach), 249 DEVMETHOD(device_suspend, kvm_clock_suspend), 250 DEVMETHOD(device_resume, kvm_clock_resume), 251 /* clock interface */ 252 DEVMETHOD(clock_gettime, kvm_clock_gettime), 253 DEVMETHOD(clock_settime, kvm_clock_settime), 254 255 DEVMETHOD_END 256 }; 257 258 static driver_t kvm_clock_driver = { 259 KVM_CLOCK_DEVNAME, 260 kvm_clock_methods, 261 sizeof(struct kvm_clock_softc), 262 }; 263 264 DRIVER_MODULE(kvm_clock, nexus, kvm_clock_driver, 0, 0); 265