/*- * SPDX-License-Identifier: BSD-2-Clause * * Copyright (c) 2014 Bryan Venteicher * Copyright (c) 2021 Mathieu Chouquet-Stringer * Copyright (c) 2021 Juniper Networks, Inc. * Copyright (c) 2021 Klara, Inc. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ /* * Linux KVM paravirtual clock support * * References: * - [1] https://www.kernel.org/doc/html/latest/virt/kvm/cpuid.html * - [2] https://www.kernel.org/doc/html/latest/virt/kvm/msr.html */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include "clock_if.h" #define KVM_CLOCK_DEVNAME "kvmclock" /* * Note: Chosen to be (1) above HPET's value (always 950), (2) above the TSC's * default value of 800, and (3) below the TSC's value when it supports the * "Invariant TSC" feature and is believed to be synchronized across all CPUs. */ #define KVM_CLOCK_TC_QUALITY 975 struct kvm_clock_softc { struct pvclock pvc; struct pvclock_wall_clock wc; struct pvclock_vcpu_time_info *timeinfos; u_int msr_tc; u_int msr_wc; #ifndef EARLY_AP_STARTUP int firstcpu; #endif }; static devclass_t kvm_clock_devclass; static struct pvclock_wall_clock *kvm_clock_get_wallclock(void *arg); static void kvm_clock_system_time_enable(struct kvm_clock_softc *sc, const cpuset_t *cpus); static void kvm_clock_system_time_enable_pcpu(void *arg); static struct pvclock_wall_clock * kvm_clock_get_wallclock(void *arg) { struct kvm_clock_softc *sc = arg; wrmsr(sc->msr_wc, vtophys(&sc->wc)); return (&sc->wc); } static void kvm_clock_system_time_enable(struct kvm_clock_softc *sc, const cpuset_t *cpus) { smp_rendezvous_cpus(*cpus, NULL, kvm_clock_system_time_enable_pcpu, NULL, sc); } static void kvm_clock_system_time_enable_pcpu(void *arg) { struct kvm_clock_softc *sc = arg; /* * See [2]; the lsb of this MSR is the system time enable bit. */ wrmsr(sc->msr_tc, vtophys(&(sc->timeinfos)[curcpu]) | 1); } #ifndef EARLY_AP_STARTUP static void kvm_clock_init_smp(void *arg __unused) { devclass_t kvm_clock_devclass; cpuset_t cpus; struct kvm_clock_softc *sc; kvm_clock_devclass = devclass_find(KVM_CLOCK_DEVNAME); sc = devclass_get_softc(kvm_clock_devclass, 0); if (sc == NULL || mp_ncpus == 1) return; /* * Register with the hypervisor on all CPUs except the one that * registered in kvm_clock_attach(). */ cpus = all_cpus; KASSERT(CPU_ISSET(sc->firstcpu, &cpus), ("%s: invalid first CPU %d", __func__, sc->firstcpu)); CPU_CLR(sc->firstcpu, &cpus); kvm_clock_system_time_enable(sc, &cpus); } SYSINIT(kvm_clock, SI_SUB_SMP, SI_ORDER_ANY, kvm_clock_init_smp, NULL); #endif static void kvm_clock_identify(driver_t *driver, device_t parent) { u_int regs[4]; kvm_cpuid_get_features(regs); if ((regs[0] & (KVM_FEATURE_CLOCKSOURCE2 | KVM_FEATURE_CLOCKSOURCE)) == 0) return; if (device_find_child(parent, KVM_CLOCK_DEVNAME, -1)) return; BUS_ADD_CHILD(parent, 0, KVM_CLOCK_DEVNAME, 0); } static int kvm_clock_probe(device_t dev) { device_set_desc(dev, "KVM paravirtual clock"); return (BUS_PROBE_DEFAULT); } static int kvm_clock_attach(device_t dev) { u_int regs[4]; struct kvm_clock_softc *sc = device_get_softc(dev); bool stable_flag_supported; /* Process KVM "features" CPUID leaf content: */ kvm_cpuid_get_features(regs); if ((regs[0] & KVM_FEATURE_CLOCKSOURCE2) != 0) { sc->msr_tc = KVM_MSR_SYSTEM_TIME_NEW; sc->msr_wc = KVM_MSR_WALL_CLOCK_NEW; } else { KASSERT((regs[0] & KVM_FEATURE_CLOCKSOURCE) != 0, ("Clocksource feature flags disappeared since " "kvm_clock_identify: regs[0] %#0x.", regs[0])); sc->msr_tc = KVM_MSR_SYSTEM_TIME; sc->msr_wc = KVM_MSR_WALL_CLOCK; } stable_flag_supported = (regs[0] & KVM_FEATURE_CLOCKSOURCE_STABLE_BIT) != 0; /* Set up 'struct pvclock_vcpu_time_info' page(s): */ sc->timeinfos = (struct pvclock_vcpu_time_info *)kmem_malloc(mp_ncpus * sizeof(struct pvclock_vcpu_time_info), M_WAITOK | M_ZERO); #ifdef EARLY_AP_STARTUP kvm_clock_system_time_enable(sc, &all_cpus); #else sc->firstcpu = curcpu; kvm_clock_system_time_enable_pcpu(sc); #endif /* * Init pvclock; register KVM clock wall clock, register KVM clock * timecounter, and set up the requisite infrastructure for vDSO access * to this timecounter. * Regarding 'tc_flags': Since the KVM MSR documentation does not * specifically discuss suspend/resume scenarios, conservatively * leave 'TC_FLAGS_SUSPEND_SAFE' cleared and assume that the system * time must be re-inited in such cases. */ sc->pvc.get_wallclock = kvm_clock_get_wallclock; sc->pvc.get_wallclock_arg = sc; sc->pvc.timeinfos = sc->timeinfos; sc->pvc.stable_flag_supported = stable_flag_supported; pvclock_init(&sc->pvc, dev, KVM_CLOCK_DEVNAME, KVM_CLOCK_TC_QUALITY, 0); return (0); } static int kvm_clock_detach(device_t dev) { struct kvm_clock_softc *sc = device_get_softc(dev); return (pvclock_destroy(&sc->pvc)); } static int kvm_clock_suspend(device_t dev) { return (0); } static int kvm_clock_resume(device_t dev) { /* * See note in 'kvm_clock_attach()' regarding 'TC_FLAGS_SUSPEND_SAFE'; * conservatively assume that the system time must be re-inited in * suspend/resume scenarios. */ kvm_clock_system_time_enable(device_get_softc(dev), &all_cpus); pvclock_resume(); inittodr(time_second); return (0); } static int kvm_clock_gettime(device_t dev, struct timespec *ts) { struct kvm_clock_softc *sc = device_get_softc(dev); pvclock_gettime(&sc->pvc, ts); return (0); } static int kvm_clock_settime(device_t dev, struct timespec *ts) { /* * Even though it is not possible to set the KVM clock's wall clock, to * avoid the possibility of periodic benign error messages from * 'settime_task_func()', report success rather than, e.g., 'ENODEV'. */ return (0); } static device_method_t kvm_clock_methods[] = { DEVMETHOD(device_identify, kvm_clock_identify), DEVMETHOD(device_probe, kvm_clock_probe), DEVMETHOD(device_attach, kvm_clock_attach), DEVMETHOD(device_detach, kvm_clock_detach), DEVMETHOD(device_suspend, kvm_clock_suspend), DEVMETHOD(device_resume, kvm_clock_resume), /* clock interface */ DEVMETHOD(clock_gettime, kvm_clock_gettime), DEVMETHOD(clock_settime, kvm_clock_settime), DEVMETHOD_END }; static driver_t kvm_clock_driver = { KVM_CLOCK_DEVNAME, kvm_clock_methods, sizeof(struct kvm_clock_softc), }; DRIVER_MODULE(kvm_clock, nexus, kvm_clock_driver, kvm_clock_devclass, 0, 0);