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Message-ID: <CAFgQCTuuSx6jDy_Q-7mrqpQF0sSDiwEV+eZ-7HCV_PLxnDn-RA@mail.gmail.com>
Date:	Tue, 13 Dec 2011 17:29:50 +0800
From:	Liu ping fan <kernelfans@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org, avi@...hat.com,
	aliguori@...ibm.com, jan.kiszka@....de
Subject: Re: [PATCH v3] kvm: make vcpu life cycle separated from kvm instance

On Mon, Dec 12, 2011 at 8:54 PM, Gleb Natapov <gleb@...hat.com> wrote:
> On Mon, Dec 12, 2011 at 10:41:23AM +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 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.
>
OK, it seems unavoidable to use rculist now :-).  Just one more question, is it
useless for "case HV_X64_MSR_VP_INDEX" after adopting rculist?

Thanks and regards,
ping fan
> Also see below.
>
>> 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/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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