Re: [PATCH v3] kvm: make vcpu life cycle separated from kvm instance
From: Gleb Natapov
Date: Mon Dec 12 2011 - 07:55:09 EST
On Mon, Dec 12, 2011 at 10:41:23AM +0800, Liu Ping Fan wrote:
> From: Liu Ping Fan <pingfank@xxxxxxxxxxxxxxxxxx>
>
> Currently, vcpu can be destructed only when kvm instance destroyed.
> Change this to vcpu's destruction taken when its refcnt is zero,
> and then vcpu MUST and CAN be destroyed before kvm's destroy.
>
Please drop all printks that you add. You do not use rcu_assign_pointer()
during vcpu creation and BTW the code there is incorrect now. It assumed
that online_vcpus is never decremented so it is OK to put newly created
vcpu into kvm->vcpus[kvm->online_vcpus], but now it is not longer true.
We even have BUG_ON() to catch that which I believe you can trigger with
this patch by creating 3 vcpus, removing second one and then adding one
more. Moving to rculist would solve this of course, and will simplify
code that iterates over all vcpus too.
Also see below.
> Signed-off-by: Liu Ping Fan <pingfank@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/kvm/i8254.c | 10 ++++--
> arch/x86/kvm/i8259.c | 12 +++++--
> arch/x86/kvm/mmu.c | 7 ++--
> arch/x86/kvm/x86.c | 54 +++++++++++++++++++----------------
> include/linux/kvm_host.h | 71 ++++++++++++++++++++++++++++++++++++++++++----
> virt/kvm/irq_comm.c | 7 +++-
> virt/kvm/kvm_main.c | 62 +++++++++++++++++++++++++++++++++------
> 7 files changed, 170 insertions(+), 53 deletions(-)
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 76e3f1c..ac79598 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -289,7 +289,7 @@ static void pit_do_work(struct work_struct *work)
> struct kvm_pit *pit = container_of(work, struct kvm_pit, expired);
> struct kvm *kvm = pit->kvm;
> struct kvm_vcpu *vcpu;
> - int i;
> + struct kvm_iter it;
> struct kvm_kpit_state *ps = &pit->pit_state;
> int inject = 0;
>
> @@ -315,9 +315,13 @@ static void pit_do_work(struct work_struct *work)
> * LVT0 to NMI delivery. Other PIC interrupts are just sent to
> * VCPU0, and only if its LVT0 is in EXTINT mode.
> */
> - if (kvm->arch.vapics_in_nmi_mode > 0)
> - kvm_for_each_vcpu(i, vcpu, kvm)
> + if (kvm->arch.vapics_in_nmi_mode > 0) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> kvm_apic_nmi_wd_deliver(vcpu);
> + }
> + rcu_read_unlock();
> + }
> }
> }
>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index cac4746..2186b30 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -50,25 +50,29 @@ static void pic_unlock(struct kvm_pic *s)
> {
> bool wakeup = s->wakeup_needed;
> struct kvm_vcpu *vcpu, *found = NULL;
> - int i;
> + struct kvm *kvm = s->kvm;
> + struct kvm_iter it;
>
> s->wakeup_needed = false;
>
> spin_unlock(&s->lock);
>
> if (wakeup) {
> - kvm_for_each_vcpu(i, vcpu, s->kvm) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm)
> if (kvm_apic_accept_pic_intr(vcpu)) {
> found = vcpu;
> break;
> }
> - }
>
> - if (!found)
> + if (!found) {
> + rcu_read_unlock();
> return;
> + }
>
> kvm_make_request(KVM_REQ_EVENT, found);
> kvm_vcpu_kick(found);
> + rcu_read_unlock();
> }
> }
>
> diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
> index f1b36cf..c16887e 100644
> --- a/arch/x86/kvm/mmu.c
> +++ b/arch/x86/kvm/mmu.c
> @@ -1833,11 +1833,12 @@ static void kvm_mmu_put_page(struct kvm_mmu_page *sp, u64 *parent_pte)
>
> static void kvm_mmu_reset_last_pte_updated(struct kvm *kvm)
> {
> - int i;
> + struct kvm_iter it;
> struct kvm_vcpu *vcpu;
> -
> - kvm_for_each_vcpu(i, vcpu, kvm)
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm)
> vcpu->arch.last_pte_updated = NULL;
> + rcu_read_unlock();
> }
>
> static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c38efd7..a302470 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1831,10 +1831,15 @@ static int get_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> switch (msr) {
> case HV_X64_MSR_VP_INDEX: {
> int r;
> + struct kvm_iter it;
> struct kvm_vcpu *v;
> - kvm_for_each_vcpu(r, v, vcpu->kvm)
> + struct kvm *kvm = vcpu->kvm;
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, v, kvm) {
> if (v == vcpu)
> data = r;
> + }
> + rcu_read_unlock();
> break;
> }
> case HV_X64_MSR_EOI:
> @@ -4966,7 +4971,8 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
> struct cpufreq_freqs *freq = data;
> struct kvm *kvm;
> struct kvm_vcpu *vcpu;
> - int i, send_ipi = 0;
> + int send_ipi = 0;
> + struct kvm_iter it;
>
> /*
> * We allow guests to temporarily run on slowing clocks,
> @@ -5016,13 +5022,16 @@ static int kvmclock_cpufreq_notifier(struct notifier_block *nb, unsigned long va
>
> raw_spin_lock(&kvm_lock);
> list_for_each_entry(kvm, &vm_list, vm_list) {
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> +
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> if (vcpu->cpu != freq->cpu)
> continue;
> kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
> if (vcpu->cpu != smp_processor_id())
> send_ipi = 1;
> }
> + rcu_read_unlock();
> }
> raw_spin_unlock(&kvm_lock);
>
> @@ -6433,13 +6442,17 @@ int kvm_arch_hardware_enable(void *garbage)
> {
> struct kvm *kvm;
> struct kvm_vcpu *vcpu;
> - int i;
> + struct kvm_iter it;
>
> kvm_shared_msr_cpu_online();
> - list_for_each_entry(kvm, &vm_list, vm_list)
> - kvm_for_each_vcpu(i, vcpu, kvm)
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> if (vcpu->cpu == smp_processor_id())
> kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
> + }
> + rcu_read_unlock();
> + }
> return kvm_x86_ops->hardware_enable(garbage);
> }
>
> @@ -6560,27 +6573,19 @@ static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
> vcpu_put(vcpu);
> }
>
> -static void kvm_free_vcpus(struct kvm *kvm)
> -{
> - unsigned int i;
> - struct kvm_vcpu *vcpu;
>
> - /*
> - * Unpin any mmu pages first.
> - */
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> - kvm_clear_async_pf_completion_queue(vcpu);
> - kvm_unload_vcpu_mmu(vcpu);
> - }
> - kvm_for_each_vcpu(i, vcpu, kvm)
> - kvm_arch_vcpu_free(vcpu);
>
> - mutex_lock(&kvm->lock);
> - for (i = 0; i < atomic_read(&kvm->online_vcpus); i++)
> - kvm->vcpus[i] = NULL;
> +void kvm_arch_vcpu_zap(struct work_struct *work)
> +{
> + struct kvm_vcpu *vcpu = container_of(work, struct kvm_vcpu,
> + zap_work);
> + struct kvm *kvm = vcpu->kvm;
>
> - atomic_set(&kvm->online_vcpus, 0);
> - mutex_unlock(&kvm->lock);
> + printk(KERN_INFO "%s, zap vcpu:0x%x\n", __func__, vcpu->vcpu_id);
> + kvm_clear_async_pf_completion_queue(vcpu);
> + kvm_unload_vcpu_mmu(vcpu);
> + kvm_arch_vcpu_free(vcpu);
> + kvm_put_kvm(kvm);
> }
>
> void kvm_arch_sync_events(struct kvm *kvm)
> @@ -6594,7 +6599,6 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
> kvm_iommu_unmap_guest(kvm);
> kfree(kvm->arch.vpic);
> kfree(kvm->arch.vioapic);
> - kvm_free_vcpus(kvm);
> if (kvm->arch.apic_access_page)
> put_page(kvm->arch.apic_access_page);
> if (kvm->arch.ept_identity_pagetable)
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index d526231..2faafcb 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -19,6 +19,7 @@
> #include <linux/slab.h>
> #include <linux/rcupdate.h>
> #include <linux/ratelimit.h>
> +#include <linux/atomic.h>
> #include <asm/signal.h>
>
> #include <linux/kvm.h>
> @@ -113,6 +114,8 @@ enum {
>
> struct kvm_vcpu {
> struct kvm *kvm;
> + struct rcu_head head;
> + struct work_struct zap_work;
> #ifdef CONFIG_PREEMPT_NOTIFIERS
> struct preempt_notifier preempt_notifier;
> #endif
> @@ -290,17 +293,73 @@ struct kvm {
> #define kvm_printf(kvm, fmt ...) printk(KERN_DEBUG fmt)
> #define vcpu_printf(vcpu, fmt...) kvm_printf(vcpu->kvm, fmt)
>
> +void kvm_arch_vcpu_zap(struct work_struct *work);
> +
> +/*search vcpu, must be protected by rcu_read_lock*/
> static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
> {
> + struct kvm_vcpu *vcpu;
> smp_rmb();
> - return kvm->vcpus[i];
> + vcpu = rcu_dereference(kvm->vcpus[i]);
> + return vcpu;
> +}
> +
> +/*Must be protected by RCU*/
> +struct kvm_iter {
> + struct kvm *kvm;
> + int idx;
> + int cnt;
> +};
> +
> +static inline
> +struct kvm_vcpu *kvm_fev_init(struct kvm *kvm, struct kvm_iter *it)
> +{
> + int idx, cnt;
> + struct kvm_vcpu *vcpup;
> + vcpup = NULL;
> + for (idx = 0, cnt = 0;
> + cnt < atomic_read(&kvm->online_vcpus) && idx < KVM_MAX_VCPUS;
> + idx++) {
> + vcpup = kvm_get_vcpu(kvm, idx);
> + if (unlikely(vcpup == NULL))
> + continue;
> + cnt++;
> + break;
> + }
> +
> + it->kvm = kvm;
> + it->idx = idx;
> + it->cnt = cnt;
> + return vcpup;
> +}
> +
> +static inline
> +struct kvm_vcpu *kvm_fev_next(struct kvm_iter *it)
> +{
> + int idx, cnt;
> + struct kvm_vcpu *vcpup;
> + struct kvm *kvm = it->kvm;
> +
> + vcpup = NULL;
> + for (idx = it->idx+1, cnt = it->cnt;
> + cnt < atomic_read(&kvm->online_vcpus) && idx < KVM_MAX_VCPUS;
> + idx++) {
> + vcpup = kvm_get_vcpu(kvm, idx);
> + if (unlikely(vcpup == NULL))
> + continue;
> + cnt++;
> + break;
> + }
> +
> + it->idx = idx;
> + it->cnt = cnt;
> + return vcpup;
> }
>
> -#define kvm_for_each_vcpu(idx, vcpup, kvm) \
> - for (idx = 0; \
> - idx < atomic_read(&kvm->online_vcpus) && \
> - (vcpup = kvm_get_vcpu(kvm, idx)) != NULL; \
> - idx++)
> +#define kvm_for_each_vcpu(it, vcpu, kvm) \
> + for (vcpu = kvm_fev_init(kvm, &it); \
> + vcpu; \
> + vcpu = kvm_fev_next(&it))
>
> int kvm_vcpu_init(struct kvm_vcpu *vcpu, struct kvm *kvm, unsigned id);
> void kvm_vcpu_uninit(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> index 9f614b4..87eae96 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -81,14 +81,16 @@ inline static bool kvm_is_dm_lowest_prio(struct kvm_lapic_irq *irq)
> int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> struct kvm_lapic_irq *irq)
> {
> - int i, r = -1;
> + int r = -1;
> + struct kvm_iter it;
> struct kvm_vcpu *vcpu, *lowest = NULL;
>
> if (irq->dest_mode == 0 && irq->dest_id == 0xff &&
> kvm_is_dm_lowest_prio(irq))
> printk(KERN_INFO "kvm: apic: phys broadcast and lowest prio\n");
>
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> if (!kvm_apic_present(vcpu))
> continue;
>
> @@ -111,6 +113,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> if (lowest)
> r = kvm_apic_set_irq(lowest, irq);
>
> + rcu_read_unlock();
> return r;
> }
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index d9cfb78..d28356a 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -171,7 +171,8 @@ static void ack_flush(void *_completed)
>
> static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
> {
> - int i, cpu, me;
> + int cpu, me;
> + struct kvm_iter it;
> cpumask_var_t cpus;
> bool called = true;
> struct kvm_vcpu *vcpu;
> @@ -179,7 +180,9 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
> zalloc_cpumask_var(&cpus, GFP_ATOMIC);
>
> me = get_cpu();
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> +
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> kvm_make_request(req, vcpu);
> cpu = vcpu->cpu;
>
> @@ -190,12 +193,15 @@ static bool make_all_cpus_request(struct kvm *kvm, unsigned int req)
> kvm_vcpu_exiting_guest_mode(vcpu) != OUTSIDE_GUEST_MODE)
> cpumask_set_cpu(cpu, cpus);
> }
> +
> if (unlikely(cpus == NULL))
> smp_call_function_many(cpu_online_mask, ack_flush, NULL, 1);
> else if (!cpumask_empty(cpus))
> smp_call_function_many(cpus, ack_flush, NULL, 1);
> else
> called = false;
> + rcu_read_unlock();
> +
> put_cpu();
> free_cpumask_var(cpus);
> return called;
> @@ -580,6 +586,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
> kvm_arch_free_vm(kvm);
> hardware_disable_all();
> mmdrop(mm);
> + printk(KERN_INFO "%s finished\n", __func__);
> }
>
> void kvm_get_kvm(struct kvm *kvm)
> @@ -1543,6 +1550,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> int last_boosted_vcpu = me->kvm->last_boosted_vcpu;
> int yielded = 0;
> int pass;
> + struct kvm_iter it;
> int i;
>
> /*
> @@ -1553,9 +1561,11 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> * We approximate round-robin by starting at the last boosted VCPU.
> */
> for (pass = 0; pass < 2 && !yielded; pass++) {
> - kvm_for_each_vcpu(i, vcpu, kvm) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> struct task_struct *task = NULL;
> struct pid *pid;
> + i = it.idx;
> if (!pass && i < last_boosted_vcpu) {
> i = last_boosted_vcpu;
> continue;
> @@ -1584,6 +1594,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> }
> put_task_struct(task);
> }
> + rcu_read_unlock();
> }
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);
> @@ -1620,11 +1631,23 @@ static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
> return 0;
> }
>
> +/*Can not block*/
> +static void kvm_vcpu_zap(struct rcu_head *rcu)
> +{
> + struct kvm_vcpu *vcpu = container_of(rcu, struct kvm_vcpu, head);
> + schedule_work(&vcpu->zap_work);
> +}
> +
> static int kvm_vcpu_release(struct inode *inode, struct file *filp)
> {
> struct kvm_vcpu *vcpu = filp->private_data;
> -
> - kvm_put_kvm(vcpu->kvm);
> + struct kvm *kvm = vcpu->kvm;
> + filp->private_data = NULL;
> + mutex_lock(&kvm->lock);
> + rcu_assign_pointer(kvm->vcpus[vcpu->vcpu_id], NULL);
vcpu->vcpu_id is not an index into vcpus array.
> + atomic_dec(&kvm->online_vcpus);
> + mutex_unlock(&kvm->lock);
> + call_rcu(&vcpu->head, kvm_vcpu_zap);
> return 0;
> }
>
> @@ -1646,6 +1669,16 @@ static int create_vcpu_fd(struct kvm_vcpu *vcpu)
> return anon_inode_getfd("kvm-vcpu", &kvm_vcpu_fops, vcpu, O_RDWR);
> }
>
> +static struct kvm_vcpu *kvm_vcpu_create(struct kvm *kvm, u32 id)
> +{
> + struct kvm_vcpu *vcpu;
> + vcpu = kvm_arch_vcpu_create(kvm, id);
> + if (IS_ERR(vcpu))
> + return vcpu;
> + INIT_WORK(&vcpu->zap_work, kvm_arch_vcpu_zap);
> + return vcpu;
> +}
> +
> /*
> * Creates some virtual cpus. Good luck creating more than one.
> */
> @@ -1653,8 +1686,9 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> {
> int r;
> struct kvm_vcpu *vcpu, *v;
> + struct kvm_iter it;
>
> - vcpu = kvm_arch_vcpu_create(kvm, id);
> + vcpu = kvm_vcpu_create(kvm, id);
> if (IS_ERR(vcpu))
> return PTR_ERR(vcpu);
>
> @@ -1670,11 +1704,15 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> goto unlock_vcpu_destroy;
> }
>
> - kvm_for_each_vcpu(r, v, kvm)
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, v, kvm) {
> if (v->vcpu_id == id) {
> + rcu_read_unlock();
> r = -EEXIST;
> goto unlock_vcpu_destroy;
> }
> + }
> + rcu_read_unlock();
>
> BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
>
> @@ -2593,13 +2631,17 @@ static int vcpu_stat_get(void *_offset, u64 *val)
> unsigned offset = (long)_offset;
> struct kvm *kvm;
> struct kvm_vcpu *vcpu;
> - int i;
> + struct kvm_iter it;
>
> *val = 0;
> raw_spin_lock(&kvm_lock);
> - list_for_each_entry(kvm, &vm_list, vm_list)
> - kvm_for_each_vcpu(i, vcpu, kvm)
> + list_for_each_entry(kvm, &vm_list, vm_list) {
> + rcu_read_lock();
> + kvm_for_each_vcpu(it, vcpu, kvm) {
> *val += *(u32 *)((void *)vcpu + offset);
> + }
> + rcu_read_unlock();
> + }
>
> raw_spin_unlock(&kvm_lock);
> return 0;
> --
> 1.7.4.4
--
Gleb.
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