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SubjectRe: [PATCH 1/2] kvm: make vcpu life cycle separated from kvm instance
On 11/25/2011 04:35 AM, Liu Ping Fan wrote:
> From: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
>
> Currently, vcpu can be destructed only when kvm instance destroyed.
> Change this to vcpu as a refer to kvm, and then vcpu MUST and CAN be
> destroyed before kvm's destroy. Qemu will take advantage of this to
> exit the vcpu thread if the thread is no longer in use by guest.
>
> Signed-off-by: Liu Ping Fan <pingfank@linux.vnet.ibm.com>
> ---
> arch/x86/kvm/x86.c | 28 ++++++++--------------------
> include/linux/kvm_host.h | 2 ++
> virt/kvm/kvm_main.c | 31 +++++++++++++++++++++++++++++--
> 3 files changed, 39 insertions(+), 22 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index c38efd7..ea2315a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6560,27 +6560,16 @@ 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 kref *ref)
> {
> - 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_vcpu *vcpu = container_of(ref, struct kvm_vcpu, refcount);
> + 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 +6583,6 @@ 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..fe35078 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -113,6 +113,7 @@ enum {
>
> struct kvm_vcpu {
> struct kvm *kvm;
> + struct kref refcount;
> #ifdef CONFIG_PREEMPT_NOTIFIERS
> struct preempt_notifier preempt_notifier;
> #endif
> @@ -460,6 +461,7 @@ void kvm_arch_exit(void);
> int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu);
>
> +void kvm_arch_vcpu_zap(struct kref *ref);
> void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu);
> void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu);
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index d9cfb78..f166bc8 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -580,6 +580,7 @@ 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)
> @@ -1503,6 +1504,16 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
> mark_page_dirty_in_slot(kvm, memslot, gfn);
> }
>
> +void kvm_vcpu_get(struct kvm_vcpu *vcpu)
> +{
> + kref_get(&vcpu->refcount);
> +}
> +
> +void kvm_vcpu_put(struct kvm_vcpu *vcpu)
> +{
> + kref_put(&vcpu->refcount, kvm_arch_vcpu_zap);
> +}
> +
> /*
> * The vCPU has executed a HLT instruction with in-kernel mode enabled.
> */
> @@ -1623,8 +1634,13 @@ static int kvm_vcpu_mmap(struct file *file, struct vm_area_struct *vma)
> static int kvm_vcpu_release(struct inode *inode, struct file *filp)
> {
> struct kvm_vcpu *vcpu = filp->private_data;
> + struct kvm *kvm = vcpu->kvm;
>
> - kvm_put_kvm(vcpu->kvm);
> + filp->private_data = NULL;
> + mutex_lock(&kvm->lock);
> + atomic_sub(1, &kvm->online_vcpus);
> + mutex_unlock(&kvm->lock);
> + kvm_vcpu_put(vcpu);
> return 0;
> }
>
> @@ -1646,6 +1662,17 @@ 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;
> +
> + kref_init(&vcpu->refcount);
> + return vcpu;
> +}
> +
> /*
> * Creates some virtual cpus. Good luck creating more than one.
> */
> @@ -1654,7 +1681,7 @@ static int kvm_vm_ioctl_create_vcpu(struct kvm *kvm, u32 id)
> int r;
> 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);
>

I don't think this is sufficient to actually remove a vcpu from the vcpu
table. It may be referred to from other vcpus in the local APIC code.
Practically the only thing that can accomplish this without a
substantial effort is rcu.

--
error compiling committee.c: too many arguments to function



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