linux-kernel - Re: [PATCH v1 1/7] vfio/ccw: create a parent struct

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Message-ID: <471d1f18-13b5-8e80-32aa-1598bca5bf2e@linux.ibm.com>
Date:   Fri, 28 Oct 2022 12:51:00 -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 v1 1/7] vfio/ccw: create a parent struct

On 10/19/22 12:21 PM, Eric Farman wrote:
> Move the stuff associated with the mdev parent (and thus the
> subchannel struct) into its own struct, and leave the rest in
> the existing private structure.
> 
> The subchannel will point to the parent, and the parent will point
> to the private, for the areas where one or both are needed. Further
> separation of these structs will follow.
> 
> Signed-off-by: Eric Farman <farman@...ux.ibm.com>
> ---
>  drivers/s390/cio/vfio_ccw_drv.c     | 104 ++++++++++++++++++++--------
>  drivers/s390/cio/vfio_ccw_ops.c     |   9 ++-
>  drivers/s390/cio/vfio_ccw_parent.h  |  28 ++++++++
>  drivers/s390/cio/vfio_ccw_private.h |   5 --
>  4 files changed, 112 insertions(+), 34 deletions(-)
>  create mode 100644 drivers/s390/cio/vfio_ccw_parent.h
> 
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> index 7f5402fe857a..634760ca0dea 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -20,6 +20,7 @@
>  #include "chp.h"
>  #include "ioasm.h"
>  #include "css.h"
> +#include "vfio_ccw_parent.h"
>  #include "vfio_ccw_private.h"
>  
>  struct workqueue_struct *vfio_ccw_work_q;
> @@ -36,7 +37,8 @@ debug_info_t *vfio_ccw_debug_trace_id;
>   */
>  int vfio_ccw_sch_quiesce(struct subchannel *sch)
>  {
> -	struct vfio_ccw_private *private = dev_get_drvdata(&sch->dev);
> +	struct vfio_ccw_parent *parent = dev_get_drvdata(&sch->dev);
> +	struct vfio_ccw_private *private = dev_get_drvdata(&parent->dev);
>  	DECLARE_COMPLETION_ONSTACK(completion);
>  	int iretry, ret = 0;
>  
> @@ -51,19 +53,21 @@ int vfio_ccw_sch_quiesce(struct subchannel *sch)
>  			break;
>  		}
>  
> -		/*
> -		 * Flush all I/O and wait for
> -		 * cancel/halt/clear completion.
> -		 */
> -		private->completion = &completion;
> -		spin_unlock_irq(sch->lock);
> +		if (private) {

Is it valid to ever reach this code with private == NULL?  If no, then this should probably be a WARN_ON upfront?

> +			/*
> +			 * Flush all I/O and wait for
> +			 * cancel/halt/clear completion.
> +			 */
> +			private->completion = &completion;
> +			spin_unlock_irq(sch->lock);
>  
> -		if (ret == -EBUSY)
> -			wait_for_completion_timeout(&completion, 3*HZ);
> +			if (ret == -EBUSY)
> +				wait_for_completion_timeout(&completion, 3*HZ);
>  
> -		private->completion = NULL;
> -		flush_workqueue(vfio_ccw_work_q);
> -		spin_lock_irq(sch->lock);
> +			private->completion = NULL;
> +			flush_workqueue(vfio_ccw_work_q);
> +			spin_lock_irq(sch->lock);
> +		}
>  		ret = cio_disable_subchannel(sch);
>  	} while (ret == -EBUSY);
>  

.. snip ..

> diff --git a/drivers/s390/cio/vfio_ccw_parent.h b/drivers/s390/cio/vfio_ccw_parent.h
> new file mode 100644
> index 000000000000..834c00077802
> --- /dev/null
> +++ b/drivers/s390/cio/vfio_ccw_parent.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * MDEV Parent contents for vfio_ccw driver
> + *
> + * Copyright IBM Corp. 2022
> + */
> +
> +#ifndef _VFIO_CCW_PARENT_H_
> +#define _VFIO_CCW_PARENT_H_
> +
> +#include <linux/mdev.h>
> +
> +/**
> + * struct vfio_ccw_parent
> + *
> + * @dev: embedded device struct
> + * @parent: parent data structures for mdevs created
> + * @mdev_type(s): identifying information for mdevs created
> + */
> +struct vfio_ccw_parent {
> +	struct device		dev;
> +
> +	struct mdev_parent	parent;
> +	struct mdev_type	mdev_type;
> +	struct mdev_type	*mdev_types[1];
> +};

Structure itself seems fine, but any reason we need a new file for it?