| /* |
| * QEMU KVM support, paravirtual clock device |
| * |
| * Copyright (C) 2011 Siemens AG |
| * |
| * Authors: |
| * Jan Kiszka <jan.kiszka@siemens.com> |
| * |
| * This work is licensed under the terms of the GNU GPL version 2. |
| * See the COPYING file in the top-level directory. |
| * |
| * Contributions after 2012-01-13 are licensed under the terms of the |
| * GNU GPL, version 2 or (at your option) any later version. |
| */ |
| |
| #include "qemu/osdep.h" |
| #include "cpu.h" |
| #include "qemu/host-utils.h" |
| #include "qemu/module.h" |
| #include "sysemu/sysemu.h" |
| #include "sysemu/kvm.h" |
| #include "sysemu/hw_accel.h" |
| #include "kvm_i386.h" |
| #include "migration/vmstate.h" |
| #include "hw/sysbus.h" |
| #include "hw/kvm/clock.h" |
| #include "hw/qdev-properties.h" |
| #include "qapi/error.h" |
| |
| #include <linux/kvm.h> |
| #include "standard-headers/asm-x86/kvm_para.h" |
| |
| #define TYPE_KVM_CLOCK "kvmclock" |
| #define KVM_CLOCK(obj) OBJECT_CHECK(KVMClockState, (obj), TYPE_KVM_CLOCK) |
| |
| typedef struct KVMClockState { |
| /*< private >*/ |
| SysBusDevice busdev; |
| /*< public >*/ |
| |
| uint64_t clock; |
| bool clock_valid; |
| |
| /* whether machine type supports reliable KVM_GET_CLOCK */ |
| bool mach_use_reliable_get_clock; |
| |
| /* whether the 'clock' value was obtained in a host with |
| * reliable KVM_GET_CLOCK */ |
| bool clock_is_reliable; |
| } KVMClockState; |
| |
| struct pvclock_vcpu_time_info { |
| uint32_t version; |
| uint32_t pad0; |
| uint64_t tsc_timestamp; |
| uint64_t system_time; |
| uint32_t tsc_to_system_mul; |
| int8_t tsc_shift; |
| uint8_t flags; |
| uint8_t pad[2]; |
| } __attribute__((__packed__)); /* 32 bytes */ |
| |
| static uint64_t kvmclock_current_nsec(KVMClockState *s) |
| { |
| CPUState *cpu = first_cpu; |
| CPUX86State *env = cpu->env_ptr; |
| hwaddr kvmclock_struct_pa; |
| uint64_t migration_tsc = env->tsc; |
| struct pvclock_vcpu_time_info time; |
| uint64_t delta; |
| uint64_t nsec_lo; |
| uint64_t nsec_hi; |
| uint64_t nsec; |
| |
| cpu_synchronize_state(cpu); |
| |
| if (!(env->system_time_msr & 1ULL)) { |
| /* KVM clock not active */ |
| return 0; |
| } |
| |
| kvmclock_struct_pa = env->system_time_msr & ~1ULL; |
| cpu_physical_memory_read(kvmclock_struct_pa, &time, sizeof(time)); |
| |
| assert(time.tsc_timestamp <= migration_tsc); |
| delta = migration_tsc - time.tsc_timestamp; |
| if (time.tsc_shift < 0) { |
| delta >>= -time.tsc_shift; |
| } else { |
| delta <<= time.tsc_shift; |
| } |
| |
| mulu64(&nsec_lo, &nsec_hi, delta, time.tsc_to_system_mul); |
| nsec = (nsec_lo >> 32) | (nsec_hi << 32); |
| return nsec + time.system_time; |
| } |
| |
| static void kvm_update_clock(KVMClockState *s) |
| { |
| struct kvm_clock_data data; |
| int ret; |
| |
| ret = kvm_vm_ioctl(kvm_state, KVM_GET_CLOCK, &data); |
| if (ret < 0) { |
| fprintf(stderr, "KVM_GET_CLOCK failed: %s\n", strerror(ret)); |
| abort(); |
| } |
| s->clock = data.clock; |
| |
| /* If kvm_has_adjust_clock_stable() is false, KVM_GET_CLOCK returns |
| * essentially CLOCK_MONOTONIC plus a guest-specific adjustment. This |
| * can drift from the TSC-based value that is computed by the guest, |
| * so we need to go through kvmclock_current_nsec(). If |
| * kvm_has_adjust_clock_stable() is true, and the flags contain |
| * KVM_CLOCK_TSC_STABLE, then KVM_GET_CLOCK returns a TSC-based value |
| * and kvmclock_current_nsec() is not necessary. |
| * |
| * Here, however, we need not check KVM_CLOCK_TSC_STABLE. This is because: |
| * |
| * - if the host has disabled the kvmclock master clock, the guest already |
| * has protection against time going backwards. This "safety net" is only |
| * absent when kvmclock is stable; |
| * |
| * - therefore, we can replace a check like |
| * |
| * if last KVM_GET_CLOCK was not reliable then |
| * read from memory |
| * |
| * with |
| * |
| * if last KVM_GET_CLOCK was not reliable && masterclock is enabled |
| * read from memory |
| * |
| * However: |
| * |
| * - if kvm_has_adjust_clock_stable() returns false, the left side is |
| * always true (KVM_GET_CLOCK is never reliable), and the right side is |
| * unknown (because we don't have data.flags). We must assume it's true |
| * and read from memory. |
| * |
| * - if kvm_has_adjust_clock_stable() returns true, the result of the && |
| * is always false (masterclock is enabled iff KVM_GET_CLOCK is reliable) |
| * |
| * So we can just use this instead: |
| * |
| * if !kvm_has_adjust_clock_stable() then |
| * read from memory |
| */ |
| s->clock_is_reliable = kvm_has_adjust_clock_stable(); |
| } |
| |
| static void do_kvmclock_ctrl(CPUState *cpu, run_on_cpu_data data) |
| { |
| int ret = kvm_vcpu_ioctl(cpu, KVM_KVMCLOCK_CTRL, 0); |
| |
| if (ret && ret != -EINVAL) { |
| fprintf(stderr, "%s: %s\n", __func__, strerror(-ret)); |
| } |
| } |
| |
| static void kvmclock_vm_state_change(void *opaque, int running, |
| RunState state) |
| { |
| KVMClockState *s = opaque; |
| CPUState *cpu; |
| int cap_clock_ctrl = kvm_check_extension(kvm_state, KVM_CAP_KVMCLOCK_CTRL); |
| int ret; |
| |
| if (running) { |
| struct kvm_clock_data data = {}; |
| |
| /* |
| * If the host where s->clock was read did not support reliable |
| * KVM_GET_CLOCK, read kvmclock value from memory. |
| */ |
| if (!s->clock_is_reliable) { |
| uint64_t pvclock_via_mem = kvmclock_current_nsec(s); |
| /* We can't rely on the saved clock value, just discard it */ |
| if (pvclock_via_mem) { |
| s->clock = pvclock_via_mem; |
| } |
| } |
| |
| s->clock_valid = false; |
| |
| data.clock = s->clock; |
| ret = kvm_vm_ioctl(kvm_state, KVM_SET_CLOCK, &data); |
| if (ret < 0) { |
| fprintf(stderr, "KVM_SET_CLOCK failed: %s\n", strerror(ret)); |
| abort(); |
| } |
| |
| if (!cap_clock_ctrl) { |
| return; |
| } |
| CPU_FOREACH(cpu) { |
| run_on_cpu(cpu, do_kvmclock_ctrl, RUN_ON_CPU_NULL); |
| } |
| } else { |
| |
| if (s->clock_valid) { |
| return; |
| } |
| |
| kvm_synchronize_all_tsc(); |
| |
| kvm_update_clock(s); |
| /* |
| * If the VM is stopped, declare the clock state valid to |
| * avoid re-reading it on next vmsave (which would return |
| * a different value). Will be reset when the VM is continued. |
| */ |
| s->clock_valid = true; |
| } |
| } |
| |
| static void kvmclock_realize(DeviceState *dev, Error **errp) |
| { |
| KVMClockState *s = KVM_CLOCK(dev); |
| |
| if (!kvm_enabled()) { |
| error_setg(errp, "kvmclock device requires KVM"); |
| return; |
| } |
| |
| kvm_update_clock(s); |
| |
| qemu_add_vm_change_state_handler(kvmclock_vm_state_change, s); |
| } |
| |
| static bool kvmclock_clock_is_reliable_needed(void *opaque) |
| { |
| KVMClockState *s = opaque; |
| |
| return s->mach_use_reliable_get_clock; |
| } |
| |
| static const VMStateDescription kvmclock_reliable_get_clock = { |
| .name = "kvmclock/clock_is_reliable", |
| .version_id = 1, |
| .minimum_version_id = 1, |
| .needed = kvmclock_clock_is_reliable_needed, |
| .fields = (VMStateField[]) { |
| VMSTATE_BOOL(clock_is_reliable, KVMClockState), |
| VMSTATE_END_OF_LIST() |
| } |
| }; |
| |
| /* |
| * When migrating, assume the source has an unreliable |
| * KVM_GET_CLOCK unless told otherwise. |
| */ |
| static int kvmclock_pre_load(void *opaque) |
| { |
| KVMClockState *s = opaque; |
| |
| s->clock_is_reliable = false; |
| |
| return 0; |
| } |
| |
| /* |
| * When migrating, read the clock just before migration, |
| * so that the guest clock counts during the events |
| * between: |
| * |
| * * vm_stop() |
| * * |
| * * pre_save() |
| * |
| * This reduces kvmclock difference on migration from 5s |
| * to 0.1s (when max_downtime == 5s), because sending the |
| * final pages of memory (which happens between vm_stop() |
| * and pre_save()) takes max_downtime. |
| */ |
| static int kvmclock_pre_save(void *opaque) |
| { |
| KVMClockState *s = opaque; |
| |
| kvm_update_clock(s); |
| |
| return 0; |
| } |
| |
| static const VMStateDescription kvmclock_vmsd = { |
| .name = "kvmclock", |
| .version_id = 1, |
| .minimum_version_id = 1, |
| .pre_load = kvmclock_pre_load, |
| .pre_save = kvmclock_pre_save, |
| .fields = (VMStateField[]) { |
| VMSTATE_UINT64(clock, KVMClockState), |
| VMSTATE_END_OF_LIST() |
| }, |
| .subsections = (const VMStateDescription * []) { |
| &kvmclock_reliable_get_clock, |
| NULL |
| } |
| }; |
| |
| static Property kvmclock_properties[] = { |
| DEFINE_PROP_BOOL("x-mach-use-reliable-get-clock", KVMClockState, |
| mach_use_reliable_get_clock, true), |
| DEFINE_PROP_END_OF_LIST(), |
| }; |
| |
| static void kvmclock_class_init(ObjectClass *klass, void *data) |
| { |
| DeviceClass *dc = DEVICE_CLASS(klass); |
| |
| dc->realize = kvmclock_realize; |
| dc->vmsd = &kvmclock_vmsd; |
| dc->props = kvmclock_properties; |
| } |
| |
| static const TypeInfo kvmclock_info = { |
| .name = TYPE_KVM_CLOCK, |
| .parent = TYPE_SYS_BUS_DEVICE, |
| .instance_size = sizeof(KVMClockState), |
| .class_init = kvmclock_class_init, |
| }; |
| |
| /* Note: Must be called after VCPU initialization. */ |
| void kvmclock_create(void) |
| { |
| X86CPU *cpu = X86_CPU(first_cpu); |
| |
| if (kvm_enabled() && |
| cpu->env.features[FEAT_KVM] & ((1ULL << KVM_FEATURE_CLOCKSOURCE) | |
| (1ULL << KVM_FEATURE_CLOCKSOURCE2))) { |
| sysbus_create_simple(TYPE_KVM_CLOCK, -1, NULL); |
| } |
| } |
| |
| static void kvmclock_register_types(void) |
| { |
| type_register_static(&kvmclock_info); |
| } |
| |
| type_init(kvmclock_register_types) |