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Date: Mon, 26 Dec 2011 13:09:43 +0200
From: Gleb Natapov <gleb@...hat.com>
To: Liu Ping Fan <kernelfans@...il.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com,
aliguori@...ibm.com, mtosatti@...hat.com, jan.kiszka@....de
Subject: Re: [PATCH v5] kvm: make vcpu life cycle separated from kvm instance
On Sat, Dec 17, 2011 at 11:19:35AM +0800, Liu Ping Fan wrote:
> From: Liu Ping Fan <pingfank@...ux.vnet.ibm.com>
>
> Currently, vcpu can be destructed only when kvm instance destroyed.
> Change this to vcpu's destruction before kvm instance, so vcpu MUST
> and CAN be destroyed before kvm's destroy.
>
> Signed-off-by: Liu Ping Fan <pingfank@...ux.vnet.ibm.com>
> ---
> arch/x86/kvm/i8254.c | 10 +++--
> arch/x86/kvm/i8259.c | 12 ++++--
> arch/x86/kvm/x86.c | 53 +++++++++++------------
> include/linux/kvm_host.h | 20 ++++-----
> virt/kvm/irq_comm.c | 6 ++-
> virt/kvm/kvm_main.c | 106 ++++++++++++++++++++++++++++++++++-----------
> 6 files changed, 132 insertions(+), 75 deletions(-)
>
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 76e3f1c..a3a5506 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -289,9 +289,8 @@ 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_kpit_state *ps = &pit->pit_state;
> - int inject = 0;
> + int idx, inject = 0;
>
> /* Try to inject pending interrupts when
> * last one has been acked.
> @@ -315,9 +314,12 @@ 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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm)
> kvm_apic_nmi_wd_deliver(vcpu);
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> + }
> }
> }
>
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index cac4746..5ef5c05 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;
> + int idx;
>
> s->wakeup_needed = false;
>
> spin_unlock(&s->lock);
>
> if (wakeup) {
> - kvm_for_each_vcpu(i, vcpu, s->kvm) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm)
> if (kvm_apic_accept_pic_intr(vcpu)) {
> found = vcpu;
> break;
> }
> - }
>
> - if (!found)
> + if (!found) {
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> return;
> + }
>
> kvm_make_request(KVM_REQ_EVENT, found);
> kvm_vcpu_kick(found);
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> }
> }
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 23c93fe..b79739d 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1774,14 +1774,20 @@ static int get_msr_hyperv_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> static int get_msr_hyperv(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
> {
> u64 data = 0;
> + int idx;
>
> switch (msr) {
> case HV_X64_MSR_VP_INDEX: {
> - int r;
> + int r = 0;
> struct kvm_vcpu *v;
> - kvm_for_each_vcpu(r, v, vcpu->kvm)
> + struct kvm *kvm = vcpu->kvm;
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(v, vcpu->kvm) {
> if (v == vcpu)
> data = r;
> + r++;
> + }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> break;
> }
> case HV_X64_MSR_EOI:
> @@ -4529,7 +4535,7 @@ 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 idx, send_ipi = 0;
>
> /*
> * We allow guests to temporarily run on slowing clocks,
> @@ -4579,13 +4585,16 @@ 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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(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;
> }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> +
> }
> raw_spin_unlock(&kvm_lock);
>
> @@ -5866,13 +5875,17 @@ int kvm_arch_hardware_enable(void *garbage)
> {
> struct kvm *kvm;
> struct kvm_vcpu *vcpu;
> - int i;
> + int idx;
>
> 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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm) {
> if (vcpu->cpu == smp_processor_id())
> kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
> + }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> + }
> return kvm_x86_ops->hardware_enable(garbage);
> }
>
> @@ -5989,27 +6002,14 @@ static void kvm_unload_vcpu_mmu(struct kvm_vcpu *vcpu)
> vcpu_put(vcpu);
> }
>
> -static void kvm_free_vcpus(struct kvm *kvm)
> +void kvm_arch_vcpu_zap(struct kvm_vcpu *vcpu)
> {
> - 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;
> + struct kvm *kvm = vcpu->kvm;
>
> - atomic_set(&kvm->online_vcpus, 0);
> - mutex_unlock(&kvm->lock);
> + 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)
> @@ -6023,7 +6023,6 @@ 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 8c5c303..ab22828 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -115,6 +115,7 @@ enum {
>
> struct kvm_vcpu {
> struct kvm *kvm;
> + struct list_head list;
> #ifdef CONFIG_PREEMPT_NOTIFIERS
> struct preempt_notifier preempt_notifier;
> #endif
> @@ -249,13 +250,15 @@ struct kvm {
> struct mm_struct *mm; /* userspace tied to this vm */
> struct kvm_memslots *memslots;
> struct srcu_struct srcu;
> + struct srcu_struct srcu_vcpus;
> +
> #ifdef CONFIG_KVM_APIC_ARCHITECTURE
> u32 bsp_vcpu_id;
> struct kvm_vcpu *bsp_vcpu;
Rebase to latest kvm.git.
> #endif
> - struct kvm_vcpu *vcpus[KVM_MAX_VCPUS];
> + struct list_head vcpus;
> atomic_t online_vcpus;
> - int last_boosted_vcpu;
> + struct kvm_vcpu *last_boosted_vcpu;
> struct list_head vm_list;
> struct mutex lock;
> struct kvm_io_bus *buses[KVM_NR_BUSES];
> @@ -302,17 +305,10 @@ struct kvm {
> #define kvm_printf(kvm, fmt ...) printk(KERN_DEBUG fmt)
> #define vcpu_printf(vcpu, fmt...) kvm_printf(vcpu->kvm, fmt)
>
> -static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
> -{
> - smp_rmb();
> - return kvm->vcpus[i];
> -}
> +void kvm_arch_vcpu_zap(struct kvm_vcpu *vcpu);
>
> -#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(vcpu, kvm) \
> + list_for_each_entry_rcu(vcpu, &kvm->vcpus, list)
>
> #define kvm_for_each_memslot(memslot, slots) \
> for (memslot = &slots->memslots[0]; \
> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> index 9f614b4..78dc97c 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -81,14 +81,15 @@ 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 idx, r = -1;
> 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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm) {
> if (!kvm_apic_present(vcpu))
> continue;
>
> @@ -111,6 +112,7 @@ int kvm_irq_delivery_to_apic(struct kvm *kvm, struct kvm_lapic *src,
> if (lowest)
> r = kvm_apic_set_irq(lowest, irq);
>
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> return r;
> }
>
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index e289486..ec0c920 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -171,7 +171,7 @@ 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, idx;
> cpumask_var_t cpus;
> bool called = true;
> struct kvm_vcpu *vcpu;
> @@ -179,7 +179,8 @@ 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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm) {
> kvm_make_request(req, vcpu);
> cpu = vcpu->cpu;
>
> @@ -190,12 +191,15 @@ 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);
> }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> +
> 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;
> +
> put_cpu();
> free_cpumask_var(cpus);
> return called;
> @@ -477,6 +481,8 @@ static struct kvm *kvm_create_vm(void)
> kvm_init_memslots_id(kvm);
> if (init_srcu_struct(&kvm->srcu))
> goto out_err_nosrcu;
> + if (init_srcu_struct(&kvm->srcu_vcpus))
> + goto out_err_nosrcu_vcpus;
> for (i = 0; i < KVM_NR_BUSES; i++) {
> kvm->buses[i] = kzalloc(sizeof(struct kvm_io_bus),
> GFP_KERNEL);
> @@ -500,10 +506,13 @@ static struct kvm *kvm_create_vm(void)
> raw_spin_lock(&kvm_lock);
> list_add(&kvm->vm_list, &vm_list);
> raw_spin_unlock(&kvm_lock);
> + INIT_LIST_HEAD(&kvm->vcpus);
>
> return kvm;
>
> out_err:
> + cleanup_srcu_struct(&kvm->srcu_vcpus);
> +out_err_nosrcu_vcpus:
> cleanup_srcu_struct(&kvm->srcu);
> out_err_nosrcu:
> hardware_disable_all();
> @@ -587,6 +596,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
> kvm_arch_destroy_vm(kvm);
> kvm_free_physmem(kvm);
> cleanup_srcu_struct(&kvm->srcu);
> + cleanup_srcu_struct(&kvm->srcu_vcpus);
> kvm_arch_free_vm(kvm);
> hardware_disable_all();
> mmdrop(mm);
> @@ -1593,11 +1603,9 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> {
> struct kvm *kvm = me->kvm;
> struct kvm_vcpu *vcpu;
> - int last_boosted_vcpu = me->kvm->last_boosted_vcpu;
> - int yielded = 0;
> - int pass;
> - int i;
> -
> + struct task_struct *task = NULL;
> + struct pid *pid;
> + int pass, firststart, lastone, yielded, idx;
> /*
> * We boost the priority of a VCPU that is runnable but not
> * currently running, because it got preempted by something
> @@ -1605,15 +1613,22 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> * VCPU is holding the lock that we need and will release it.
> * 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) {
> - struct task_struct *task = NULL;
> - struct pid *pid;
> - if (!pass && i < last_boosted_vcpu) {
> - i = last_boosted_vcpu;
> + for (pass = 0, firststart = 0; pass < 2 && !yielded; pass++) {
> +
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm) {
> + if (!pass && !firststart &&
> + vcpu != kvm->last_boosted_vcpu &&
> + kvm->last_boosted_vcpu != NULL) {
> + vcpu = kvm->last_boosted_vcpu;
You access last_boosted_vcpu as if it is protected by srcu, but it
isn't. kvm_vcpu_release() changes it after synchronize_srcu_expedited()
call.
I do not like this last_boosted_vcpu pointer much. May be we can rid of
it by remembering last apic_id and searching for it each time we enter
the function. I do not think this function is to performance sensitive.
We enter here when vcpu is spinning anyway.
> + firststart = 1;
> continue;
> - } else if (pass && i > last_boosted_vcpu)
> + } else if (pass && !lastone) {
> + if (vcpu == kvm->last_boosted_vcpu)
> + lastone = 1;
> + } else if (pass && lastone)
> break;
> +
> if (vcpu == me)
> continue;
> if (waitqueue_active(&vcpu->wq))
> @@ -1629,15 +1644,20 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me)
> put_task_struct(task);
> continue;
> }
> +
> if (yield_to(task, 1)) {
> put_task_struct(task);
> - kvm->last_boosted_vcpu = i;
> + mutex_lock(&kvm->lock);
> + kvm->last_boosted_vcpu = vcpu;
> + mutex_unlock(&kvm->lock);
> yielded = 1;
> break;
> }
> put_task_struct(task);
> }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> }
> +
> }
> EXPORT_SYMBOL_GPL(kvm_vcpu_on_spin);
>
> @@ -1673,11 +1693,30 @@ static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
> return 0;
> }
>
> +static void kvm_vcpu_zap(struct kvm_vcpu *vcpu)
> +{
> + kvm_arch_vcpu_zap(vcpu);
> +}
> +
> static int kvm_vcpu_release(struct inode *inode, struct file *filp)
> {
> struct kvm_vcpu *vcpu = filp->private_data;
> + struct kvm *kvm = vcpu->kvm;
> + filp->private_data = NULL;
> +
> + mutex_lock(&kvm->lock);
> + list_del_rcu(&vcpu->list);
> + atomic_dec(&kvm->online_vcpus);
> + mutex_unlock(&kvm->lock);
> + synchronize_srcu_expedited(&kvm->srcu_vcpus);
> +
> + mutex_lock(&kvm->lock);
> + if (kvm->last_boosted_vcpu == vcpu)
> + kvm->last_boosted_vcpu = NULL;
> + mutex_unlock(&kvm->lock);
>
> - kvm_put_kvm(vcpu->kvm);
> + /*vcpu is out of list,drop it safely*/
> + kvm_vcpu_zap(vcpu);
> return 0;
> }
>
> @@ -1699,15 +1738,25 @@ 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_LIST_HEAD(&vcpu->list);
> + return vcpu;
> +}
> +
> /*
> * Creates some virtual cpus. Good luck creating more than one.
> */
> static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> {
> - int r;
> + int r, idx;
> struct kvm_vcpu *vcpu, *v;
>
> - vcpu = kvm_arch_vcpu_create(kvm, id);
> + vcpu = kvm_vcpu_create(kvm, id);
> if (IS_ERR(vcpu))
> return PTR_ERR(vcpu);
>
> @@ -1723,13 +1772,15 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> goto unlock_vcpu_destroy;
> }
>
> - kvm_for_each_vcpu(r, v, kvm)
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(v, kvm) {
> if (v->vcpu_id == id) {
> r = -EEXIST;
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> goto unlock_vcpu_destroy;
> }
> -
> - BUG_ON(kvm->vcpus[atomic_read(&kvm->online_vcpus)]);
> + }
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
>
> /* Now it's all set up, let userspace reach it */
> kvm_get_kvm(kvm);
> @@ -1739,8 +1790,8 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> goto unlock_vcpu_destroy;
> }
>
> - kvm->vcpus[atomic_read(&kvm->online_vcpus)] = vcpu;
> - smp_wmb();
> + /*Protected by kvm->lock*/
> + list_add_rcu(&vcpu->list, &kvm->vcpus);
> atomic_inc(&kvm->online_vcpus);
>
> #ifdef CONFIG_KVM_APIC_ARCHITECTURE
> @@ -2645,13 +2696,16 @@ static int vcpu_stat_get(void *_offset, u64 *val)
> unsigned offset = (long)_offset;
> struct kvm *kvm;
> struct kvm_vcpu *vcpu;
> - int i;
> + int idx;
>
> *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) {
> + idx = srcu_read_lock(&kvm->srcu_vcpus);
> + kvm_for_each_vcpu(vcpu, kvm)
> *val += *(u32 *)((void *)vcpu + offset);
> + srcu_read_unlock(&kvm->srcu_vcpus, idx);
> + }
>
> raw_spin_unlock(&kvm_lock);
> return 0;
> --
> 1.7.4.4
--
Gleb.
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