linux-kernel - Re: [PATCH v2 5/7] vfio/ccw: remove release completion

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Date:   Thu, 3 Nov 2022 19:24:16 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Eric Farman <farman@...ux.ibm.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Kevin Tian <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>
Cc:     Zhenyu Wang <zhenyuw@...ux.intel.com>,
        Zhi Wang <zhi.a.wang@...el.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Halil Pasic <pasic@...ux.ibm.com>,
        Vineeth Vijayan <vneethv@...ux.ibm.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>,
        Tony Krowiak <akrowiak@...ux.ibm.com>,
        Jason Herne <jjherne@...ux.ibm.com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        Diana Craciun <diana.craciun@....nxp.com>,
        Eric Auger <eric.auger@...hat.com>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Abhishek Sahu <abhsahu@...dia.com>,
        Yishai Hadas <yishaih@...dia.com>,
        intel-gvt-dev@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org
Subject: Re: [PATCH v2 5/7] vfio/ccw: remove release completion

On 11/2/22 11:01 AM, Eric Farman wrote:
> There's enough separation between the parent and private structs now,
> that it is fine to remove the release completion hack.
> 
> Signed-off-by: Eric Farman <farman@...ux.ibm.com>
> Reviewed-by: Kevin Tian <kevin.tian@...el.com>

Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>

> ---
>  drivers/s390/cio/vfio_ccw_ops.c     | 14 +-------------
>  drivers/s390/cio/vfio_ccw_private.h |  3 ---
>  2 files changed, 1 insertion(+), 16 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c b/drivers/s390/cio/vfio_ccw_ops.c
> index e45d4acb109b..8a929a9cf3c6 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -54,7 +54,6 @@ static int vfio_ccw_mdev_init_dev(struct vfio_device *vdev)
>  	INIT_LIST_HEAD(&private->crw);
>  	INIT_WORK(&private->io_work, vfio_ccw_sch_io_todo);
>  	INIT_WORK(&private->crw_work, vfio_ccw_crw_todo);
> -	init_completion(&private->release_comp);
>  
>  	private->cp.guest_cp = kcalloc(CCWCHAIN_LEN_MAX, sizeof(struct ccw1),
>  				       GFP_KERNEL);
> @@ -137,7 +136,7 @@ static void vfio_ccw_mdev_release_dev(struct vfio_device *vdev)
>  	struct vfio_ccw_private *private =
>  		container_of(vdev, struct vfio_ccw_private, vdev);
>  
> -	complete(&private->release_comp);
> +	vfio_ccw_free_private(private);
>  }
>  
>  static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
> @@ -155,17 +154,6 @@ static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
>  
>  	dev_set_drvdata(&parent->dev, NULL);
>  	vfio_put_device(&private->vdev);
> -	/*
> -	 * Wait for all active references on mdev are released so it
> -	 * is safe to defer kfree() to a later point.
> -	 *
> -	 * TODO: the clean fix is to split parent/mdev info from ccw
> -	 * private structure so each can be managed in its own life
> -	 * cycle.
> -	 */
> -	wait_for_completion(&private->release_comp);
> -
> -	vfio_ccw_free_private(private);
>  }
>  
>  static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
> diff --git a/drivers/s390/cio/vfio_ccw_private.h b/drivers/s390/cio/vfio_ccw_private.h
> index 747aba5f5272..2278fd38d34e 100644
> --- a/drivers/s390/cio/vfio_ccw_private.h
> +++ b/drivers/s390/cio/vfio_ccw_private.h
> @@ -102,7 +102,6 @@ struct vfio_ccw_parent {
>   * @req_trigger: eventfd ctx for signaling userspace to return device
>   * @io_work: work for deferral process of I/O handling
>   * @crw_work: work for deferral process of CRW handling
> - * @release_comp: synchronization helper for vfio device release
>   */
>  struct vfio_ccw_private {
>  	struct vfio_device vdev;
> @@ -126,8 +125,6 @@ struct vfio_ccw_private {
>  	struct eventfd_ctx	*req_trigger;
>  	struct work_struct	io_work;
>  	struct work_struct	crw_work;
> -
> -	struct completion	release_comp;
>  } __aligned(8);
>  
>  int vfio_ccw_sch_quiesce(struct subchannel *sch);