Re: [PATCH] KVM: arm/arm64: kvm_arch_destroy_vm cleanups

[Christoffer Dall <cdall@linaro.org>]

Hi Drew,

On Mon, Nov 27, 2017 at 07:17:18PM +0100, Andrew Jones wrote:
> Recently commit b2c9a85dd75a ("KVM: arm/arm64: vgic: Move
> kvm_vgic_destroy call around") caught my eye. When I looked closer I
> saw that while it made the code saner, it wasn't changing anything.
> kvm_for_each_vcpu() checks for NULL kvm->vcpus[i], so there wasn't
> a NULL dereference being fixed, and because kvm_vgic_vcpu_destroy()
> was called by kvm_arch_vcpu_free() it was still getting called, just
> not by kvm_vgic_destroy() as intended. But now the call from
> kvm_arch_vcpu_free() is redundant, and while currently harmless, it
> should be removed in case kvm_vgic_vcpu_destroy() were ever to
> want to reference vgic state, as kvm_vgic_destroy() now comes before
> kvm_arch_vcpu_free(). Additionally the other architectures set
> kvm->online_vcpus to zero after freeing them. We might as well do
> that for ARM too.

Could this commit message be rewritten to:

  kvm_vgic_vcpu_destroy already gets called from kvm_vgic_destroy for
  each vcpu, so we don't have to call it from kvm_arch_vcpu_free.

  Additionally the other architectures set kvm->online_vcpus to zero
  after freeing them. We might as well do that for ARM too.

?

Thanks,
-Christoffer



> 
> Signed-off-by: Andrew Jones <drjones@redhat.com>
> ---
>  virt/kvm/arm/arm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index a6524ff27de4..c5bc79c4ccf7 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -188,6 +188,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>  			kvm->vcpus[i] = NULL;
>  		}
>  	}
> +	atomic_set(&kvm->online_vcpus, 0);
>  }
>  
>  int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> @@ -296,7 +297,6 @@ void kvm_arch_vcpu_free(struct kvm_vcpu *vcpu)
>  {
>  	kvm_mmu_free_memory_caches(vcpu);
>  	kvm_timer_vcpu_terminate(vcpu);
> -	kvm_vgic_vcpu_destroy(vcpu);
>  	kvm_pmu_vcpu_destroy(vcpu);
>  	kvm_vcpu_uninit(vcpu);
>  	kmem_cache_free(kvm_vcpu_cache, vcpu);
> -- 
> 2.13.6
>