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Subject: RE: [PATCH v4] vfio: fix potential deadlock on vfio group lock
Thread-Topic: [PATCH v4] vfio: fix potential deadlock on vfio group lock
Thread-Index: AQHZJ6vANRoQ9x2rxUaXBLM6X5ngE66iVZeQ
Date:   Tue, 17 Jan 2023 09:05:40 +0000
Message-ID: <BN9PR11MB52761554526A0278B13CB2B18CC69@BN9PR11MB5276.namprd11.prod.outlook.com>
References: <20230114000351.115444-1-mjrosato@linux.ibm.com>
In-Reply-To: <20230114000351.115444-1-mjrosato@linux.ibm.com>
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> From: Matthew Rosato <mjrosato@linux.ibm.com>
> Sent: Saturday, January 14, 2023 8:04 AM
>
>  void vfio_device_group_close(struct vfio_device *device)
>  {
> +	void (*put_kvm)(struct kvm *kvm);
> +	struct kvm *kvm;
> +
>  	mutex_lock(&device->group->group_lock);
> +	kvm =3D device->kvm;
> +	put_kvm =3D device->put_kvm;
>  	vfio_device_close(device, device->group->iommufd);
> +	if (kvm =3D=3D device->kvm)
> +		kvm =3D NULL;

Add a simple comment that this check is to detect the last close

> +void vfio_kvm_put_kvm(void (*put)(struct kvm *kvm), struct kvm *kvm)
> +{
> +	if (WARN_ON(!put))
> +		return;

also WARN_ON(!kvm)?

otherwise this looks good to me:

Reviewed-by: Kevin Tian <kevin.tian@intel.com>