linux-kernel - RE: [PATCH v2 09/14] vfio-iommufd: Add detach

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Date:   Tue, 7 Feb 2023 06:06:55 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "Liu, Yi L" <yi.l.liu@...el.com>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>
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        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
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        <shameerali.kolothum.thodi@...wei.com>,
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        <intel-gvt-dev@...ts.freedesktop.org>,
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        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>
Subject: RE: [PATCH v2 09/14] vfio-iommufd: Add detach_ioas support for
 physical VFIO devices

> From: Liu, Yi L <yi.l.liu@...el.com>
> Sent: Monday, February 6, 2023 5:05 PM
> 
> +static void __vfio_iommufd_detach(struct vfio_device *vdev)
> +{
> +	iommufd_device_detach(vdev->iommufd_device);
> +	vdev->iommufd_attached = false;
> +}
> +
>  void vfio_iommufd_physical_unbind(struct vfio_device *vdev)
>  {
>  	lockdep_assert_held(&vdev->dev_set->lock);
> 
> -	if (vdev->iommufd_attached) {
> -		iommufd_device_detach(vdev->iommufd_device);
> -		vdev->iommufd_attached = false;
> -	}
> +	if (vdev->iommufd_attached)
> +		__vfio_iommufd_detach(vdev);

I'm not sure whether this abstraction really improves things.

Just two callers. and the old code reads clearer to me which
checks a flag, does something and then clear the flag.

> @@ -74,6 +74,7 @@ struct vfio_device {
>   * @unbind_iommufd: Opposite of bind_iommufd
>   * @attach_ioas: Called when attaching device to an IOAS/HWPT managed
> by the
>   *		 bound iommufd. Undo in unbind_iommufd.

"Undo in unbind_iommufd if @detach_ioas is not called".

> + * @detach_ioas: Opposite of attach_ioas, this is for runtime undo.

remove "this is for runtime undo" which is confusing.