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-rw-r--r--hw/i386/kvm/clock.c350
1 files changed, 350 insertions, 0 deletions
diff --git a/hw/i386/kvm/clock.c b/hw/i386/kvm/clock.c
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+++ b/hw/i386/kvm/clock.c
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+/*
+ * 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 "qemu/host-utils.h"
+#include "qemu/module.h"
+#include "sysemu/kvm.h"
+#include "sysemu/runstate.h"
+#include "sysemu/hw_accel.h"
+#include "kvm/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"
+#include "qom/object.h"
+
+#define TYPE_KVM_CLOCK "kvmclock"
+OBJECT_DECLARE_SIMPLE_TYPE(KVMClockState, KVM_CLOCK)
+
+struct KVMClockState {
+ /*< private >*/
+ SysBusDevice busdev;
+ /*< public >*/
+
+ uint64_t clock;
+ bool clock_valid;
+
+ /* whether the 'clock' value was obtained in the 'paused' state */
+ bool runstate_paused;
+
+ /* 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;
+};
+
+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, bool 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;
+ }
+
+ s->runstate_paused = runstate_check(RUN_STATE_PAUSED);
+
+ 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 a running guest, 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;
+
+ if (!s->runstate_paused) {
+ 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;
+ device_class_set_props(dc, 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(bool create_always)
+{
+ X86CPU *cpu = X86_CPU(first_cpu);
+
+ if (!kvm_enabled() || !kvm_has_adjust_clock())
+ return;
+
+ if (create_always ||
+ 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)