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