linux-kernel - Re: [PATCH RFC v3 7/9] KVM: add kvm_free_vcpus and kvm_arch_free

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Date:   Tue, 22 Aug 2017 16:18:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Radim Krčmář <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-mips@...ux-mips.org, kvm-ppc@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Christoffer Dall <cdall@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Cornelia Huck <cohuck@...hat.com>,
        James Hogan <james.hogan@...tec.com>,
        Paul Mackerras <paulus@...abs.org>,
        Alexander Graf <agraf@...e.com>
Subject: Re: [PATCH RFC v3 7/9] KVM: add kvm_free_vcpus and
 kvm_arch_free_vcpus


> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 33a15e176927..0d2d8b0c785c 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -750,6 +750,23 @@ static void kvm_destroy_devices(struct kvm *kvm)
>  	}
>  }
>  
> +void kvm_free_vcpus(struct kvm *kvm)
> +{
> +	int i;
> +
> +	kvm_arch_free_vcpus(kvm);

I wonder if it would be possible to get rid of kvm_arch_free_vcpus(kvm)
completely and simply call

kvm_for_each_vcpu(i, vcpu, kvm)
	kvm_arch_vcpu_free(vcpu);

at that point.

Would certainly require some refactoring, and I am not sure if we could
modify the special mmu handling for x86 ("Unpin any mmu pages first.").
But if in doubt, that part could be moved to kvm_arch_destroy_vm(), just
before calling kvm_free_vcpus().

> +
> +	mutex_lock(&kvm->lock);
> +
> +	i = atomic_read(&kvm->online_vcpus);
> +	atomic_set(&kvm->online_vcpus, 0);

i = atomic_xchg(&kvm->online_vcpus, 0);

> +
> +	while (i--)
> +		kvm->vcpus[i] = NULL;
> +
> +	mutex_unlock(&kvm->lock);
> +}
> +
>  static void kvm_destroy_vm(struct kvm *kvm)
>  {
>  	int i;
> 


-- 

Thanks,

David