Re: [PATCH v3 04/10] vfio/ccw: Convert to use vfio_register_emulated_iommu_dev()

[Eric Farman <farman@linux.ibm.com>]

On Fri, 2021-10-01 at 14:52 -0300, Jason Gunthorpe wrote:
> This is a more complicated conversion because vfio_ccw is sharing the
> vfio_device between both the mdev_device, its vfio_device and the
> css_driver.
> 
> The mdev is a singleton, and the reason for this sharing is so the
> extra
> css_driver function callbacks to be delivered to the vfio_device
> implementation.
> 
> This keeps things as they are, with the css_driver allocating the
> singleton, not the mdev_driver. Following patches work to clean this
> further.
> 
> Embed the vfio_device in the vfio_ccw_private and instantiate it as a
> vfio_device when the mdev probes. The drvdata of both the css_device
> and
> the mdev_device point at the private, and container_of is used to get
> it
> back from the vfio_device.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

Reviewed-by: Eric Farman <farman@linux.ibm.com>

Worth noting that this particular patch depends on Alex' vfio/next
branch, which defines vfio_register_emulated_iommu_dev() and is used
below. That is alluded to in the cover letter, but of course I forgot
that point when going through the mbox.

> ---
>  drivers/s390/cio/vfio_ccw_drv.c     |  21 ++++--
>  drivers/s390/cio/vfio_ccw_ops.c     | 107 +++++++++++++++++---------
> --
>  drivers/s390/cio/vfio_ccw_private.h |   5 ++
>  3 files changed, 85 insertions(+), 48 deletions(-)
> 
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c
> b/drivers/s390/cio/vfio_ccw_drv.c
> index e32678a71644fb..0407427770955d 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -468,7 +468,7 @@ static int __init vfio_ccw_sch_init(void)
>  	vfio_ccw_work_q = create_singlethread_workqueue("vfio-ccw");
>  	if (!vfio_ccw_work_q) {
>  		ret = -ENOMEM;
> -		goto out_err;
> +		goto out_regions;
>  	}
>  
>  	vfio_ccw_io_region =
> kmem_cache_create_usercopy("vfio_ccw_io_region",
> @@ -477,7 +477,7 @@ static int __init vfio_ccw_sch_init(void)
>  					sizeof(struct ccw_io_region),
> NULL);
>  	if (!vfio_ccw_io_region) {
>  		ret = -ENOMEM;
> -		goto out_err;
> +		goto out_regions;
>  	}
>  
>  	vfio_ccw_cmd_region =
> kmem_cache_create_usercopy("vfio_ccw_cmd_region",
> @@ -486,7 +486,7 @@ static int __init vfio_ccw_sch_init(void)
>  					sizeof(struct ccw_cmd_region),
> NULL);
>  	if (!vfio_ccw_cmd_region) {
>  		ret = -ENOMEM;
> -		goto out_err;
> +		goto out_regions;
>  	}
>  
>  	vfio_ccw_schib_region =
> kmem_cache_create_usercopy("vfio_ccw_schib_region",
> @@ -496,7 +496,7 @@ static int __init vfio_ccw_sch_init(void)
>  
>  	if (!vfio_ccw_schib_region) {
>  		ret = -ENOMEM;
> -		goto out_err;
> +		goto out_regions;
>  	}
>  
>  	vfio_ccw_crw_region =
> kmem_cache_create_usercopy("vfio_ccw_crw_region",
> @@ -506,19 +506,25 @@ static int __init vfio_ccw_sch_init(void)
>  
>  	if (!vfio_ccw_crw_region) {
>  		ret = -ENOMEM;
> -		goto out_err;
> +		goto out_regions;
>  	}
>  
> +	ret = mdev_register_driver(&vfio_ccw_mdev_driver);
> +	if (ret)
> +		goto out_regions;
> +
>  	isc_register(VFIO_CCW_ISC);
>  	ret = css_driver_register(&vfio_ccw_sch_driver);
>  	if (ret) {
>  		isc_unregister(VFIO_CCW_ISC);
> -		goto out_err;
> +		goto out_driver;
>  	}
>  
>  	return ret;
>  
> -out_err:
> +out_driver:
> +	mdev_unregister_driver(&vfio_ccw_mdev_driver);
> +out_regions:
>  	vfio_ccw_destroy_regions();
>  	destroy_workqueue(vfio_ccw_work_q);
>  	vfio_ccw_debug_exit();
> @@ -528,6 +534,7 @@ static int __init vfio_ccw_sch_init(void)
>  static void __exit vfio_ccw_sch_exit(void)
>  {
>  	css_driver_unregister(&vfio_ccw_sch_driver);
> +	mdev_unregister_driver(&vfio_ccw_mdev_driver);
>  	isc_unregister(VFIO_CCW_ISC);
>  	vfio_ccw_destroy_regions();
>  	destroy_workqueue(vfio_ccw_work_q);
> diff --git a/drivers/s390/cio/vfio_ccw_ops.c
> b/drivers/s390/cio/vfio_ccw_ops.c
> index 1edbea9de0ec42..d8589afac272f1 100644
> --- a/drivers/s390/cio/vfio_ccw_ops.c
> +++ b/drivers/s390/cio/vfio_ccw_ops.c
> @@ -17,6 +17,8 @@
>  
>  #include "vfio_ccw_private.h"
>  
> +static const struct vfio_device_ops vfio_ccw_dev_ops;
> +
>  static int vfio_ccw_mdev_reset(struct vfio_ccw_private *private)
>  {
>  	struct subchannel *sch;
> @@ -111,10 +113,10 @@ static struct attribute_group
> *mdev_type_groups[] = {
>  	NULL,
>  };
>  
> -static int vfio_ccw_mdev_create(struct mdev_device *mdev)
> +static int vfio_ccw_mdev_probe(struct mdev_device *mdev)
>  {
> -	struct vfio_ccw_private *private =
> -		dev_get_drvdata(mdev_parent_dev(mdev));
> +	struct vfio_ccw_private *private = dev_get_drvdata(mdev-
> >dev.parent);
> +	int ret;
>  
>  	if (private->state == VFIO_CCW_STATE_NOT_OPER)
>  		return -ENODEV;
> @@ -122,6 +124,10 @@ static int vfio_ccw_mdev_create(struct
> mdev_device *mdev)
>  	if (atomic_dec_if_positive(&private->avail) < 0)
>  		return -EPERM;
>  
> +	memset(&private->vdev, 0, sizeof(private->vdev));
> +	vfio_init_group_dev(&private->vdev, &mdev->dev,
> +			    &vfio_ccw_dev_ops);
> +
>  	private->mdev = mdev;
>  	private->state = VFIO_CCW_STATE_IDLE;
>  
> @@ -130,19 +136,31 @@ static int vfio_ccw_mdev_create(struct
> mdev_device *mdev)
>  			   private->sch->schid.ssid,
>  			   private->sch->schid.sch_no);
>  
> +	ret = vfio_register_emulated_iommu_dev(&private->vdev);
> +	if (ret)
> +		goto err_atomic;
> +	dev_set_drvdata(&mdev->dev, private);
>  	return 0;
> +
> +err_atomic:
> +	vfio_uninit_group_dev(&private->vdev);
> +	atomic_inc(&private->avail);
> +	private->mdev = NULL;
> +	private->state = VFIO_CCW_STATE_IDLE;
> +	return ret;
>  }
>  
> -static int vfio_ccw_mdev_remove(struct mdev_device *mdev)
> +static void vfio_ccw_mdev_remove(struct mdev_device *mdev)
>  {
> -	struct vfio_ccw_private *private =
> -		dev_get_drvdata(mdev_parent_dev(mdev));
> +	struct vfio_ccw_private *private = dev_get_drvdata(mdev-
> >dev.parent);
>  
>  	VFIO_CCW_MSG_EVENT(2, "mdev %pUl, sch %x.%x.%04x: remove\n",
>  			   mdev_uuid(mdev), private->sch->schid.cssid,
>  			   private->sch->schid.ssid,
>  			   private->sch->schid.sch_no);
>  
> +	vfio_unregister_group_dev(&private->vdev);
> +
>  	if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
>  	    (private->state != VFIO_CCW_STATE_STANDBY)) {
>  		if (!vfio_ccw_sch_quiesce(private->sch))
> @@ -150,23 +168,22 @@ static int vfio_ccw_mdev_remove(struct
> mdev_device *mdev)
>  		/* The state will be NOT_OPER on error. */
>  	}
>  
> +	vfio_uninit_group_dev(&private->vdev);
>  	cp_free(&private->cp);
>  	private->mdev = NULL;
>  	atomic_inc(&private->avail);
> -
> -	return 0;
>  }
>  
> -static int vfio_ccw_mdev_open_device(struct mdev_device *mdev)
> +static int vfio_ccw_mdev_open_device(struct vfio_device *vdev)
>  {
>  	struct vfio_ccw_private *private =
> -		dev_get_drvdata(mdev_parent_dev(mdev));
> +		container_of(vdev, struct vfio_ccw_private, vdev);
>  	unsigned long events = VFIO_IOMMU_NOTIFY_DMA_UNMAP;
>  	int ret;
>  
>  	private->nb.notifier_call = vfio_ccw_mdev_notifier;
>  
> -	ret = vfio_register_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> +	ret = vfio_register_notifier(vdev->dev, VFIO_IOMMU_NOTIFY,
>  				     &events, &private->nb);
>  	if (ret)
>  		return ret;
> @@ -187,15 +204,15 @@ static int vfio_ccw_mdev_open_device(struct
> mdev_device *mdev)
>  
>  out_unregister:
>  	vfio_ccw_unregister_dev_regions(private);
> -	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> +	vfio_unregister_notifier(vdev->dev, VFIO_IOMMU_NOTIFY,
>  				 &private->nb);
>  	return ret;
>  }
>  
> -static void vfio_ccw_mdev_close_device(struct mdev_device *mdev)
> +static void vfio_ccw_mdev_close_device(struct vfio_device *vdev)
>  {
>  	struct vfio_ccw_private *private =
> -		dev_get_drvdata(mdev_parent_dev(mdev));
> +		container_of(vdev, struct vfio_ccw_private, vdev);
>  
>  	if ((private->state != VFIO_CCW_STATE_NOT_OPER) &&
>  	    (private->state != VFIO_CCW_STATE_STANDBY)) {
> @@ -206,8 +223,7 @@ static void vfio_ccw_mdev_close_device(struct
> mdev_device *mdev)
>  
>  	cp_free(&private->cp);
>  	vfio_ccw_unregister_dev_regions(private);
> -	vfio_unregister_notifier(mdev_dev(mdev), VFIO_IOMMU_NOTIFY,
> -				 &private->nb);
> +	vfio_unregister_notifier(vdev->dev, VFIO_IOMMU_NOTIFY,
> &private->nb);
>  }
>  
>  static ssize_t vfio_ccw_mdev_read_io_region(struct vfio_ccw_private
> *private,
> @@ -231,15 +247,14 @@ static ssize_t
> vfio_ccw_mdev_read_io_region(struct vfio_ccw_private *private,
>  	return ret;
>  }
>  
> -static ssize_t vfio_ccw_mdev_read(struct mdev_device *mdev,
> +static ssize_t vfio_ccw_mdev_read(struct vfio_device *vdev,
>  				  char __user *buf,
>  				  size_t count,
>  				  loff_t *ppos)
>  {
> +	struct vfio_ccw_private *private =
> +		container_of(vdev, struct vfio_ccw_private, vdev);
>  	unsigned int index = VFIO_CCW_OFFSET_TO_INDEX(*ppos);
> -	struct vfio_ccw_private *private;
> -
> -	private = dev_get_drvdata(mdev_parent_dev(mdev));
>  
>  	if (index >= VFIO_CCW_NUM_REGIONS + private->num_regions)
>  		return -EINVAL;
> @@ -284,15 +299,14 @@ static ssize_t
> vfio_ccw_mdev_write_io_region(struct vfio_ccw_private *private,
>  	return ret;
>  }
>  
> -static ssize_t vfio_ccw_mdev_write(struct mdev_device *mdev,
> +static ssize_t vfio_ccw_mdev_write(struct vfio_device *vdev,
>  				   const char __user *buf,
>  				   size_t count,
>  				   loff_t *ppos)
>  {
> +	struct vfio_ccw_private *private =
> +		container_of(vdev, struct vfio_ccw_private, vdev);
>  	unsigned int index = VFIO_CCW_OFFSET_TO_INDEX(*ppos);
> -	struct vfio_ccw_private *private;
> -
> -	private = dev_get_drvdata(mdev_parent_dev(mdev));
>  
>  	if (index >= VFIO_CCW_NUM_REGIONS + private->num_regions)
>  		return -EINVAL;
> @@ -510,12 +524,12 @@ void vfio_ccw_unregister_dev_regions(struct
> vfio_ccw_private *private)
>  	private->region = NULL;
>  }
>  
> -static ssize_t vfio_ccw_mdev_ioctl(struct mdev_device *mdev,
> +static ssize_t vfio_ccw_mdev_ioctl(struct vfio_device *vdev,
>  				   unsigned int cmd,
>  				   unsigned long arg)
>  {
>  	struct vfio_ccw_private *private =
> -		dev_get_drvdata(mdev_parent_dev(mdev));
> +		container_of(vdev, struct vfio_ccw_private, vdev);
>  	int ret = 0;
>  	unsigned long minsz;
>  
> @@ -606,37 +620,48 @@ static ssize_t vfio_ccw_mdev_ioctl(struct
> mdev_device *mdev,
>  }
>  
>  /* Request removal of the device*/
> -static void vfio_ccw_mdev_request(struct mdev_device *mdev, unsigned
> int count)
> +static void vfio_ccw_mdev_request(struct vfio_device *vdev, unsigned
> int count)
>  {
> -	struct vfio_ccw_private *private =
> dev_get_drvdata(mdev_parent_dev(mdev));
> -
> -	if (!private)
> -		return;
> +	struct vfio_ccw_private *private =
> +		container_of(vdev, struct vfio_ccw_private, vdev);
> +	struct device *dev = vdev->dev;
>  
>  	if (private->req_trigger) {
>  		if (!(count % 10))
> -			dev_notice_ratelimited(mdev_dev(private->mdev),
> +			dev_notice_ratelimited(dev,
>  					       "Relaying device request
> to user (#%u)\n",
>  					       count);
>  
>  		eventfd_signal(private->req_trigger, 1);
>  	} else if (count == 0) {
> -		dev_notice(mdev_dev(private->mdev),
> +		dev_notice(dev,
>  			   "No device request channel registered,
> blocked until released by user\n");
>  	}
>  }
>  
> +static const struct vfio_device_ops vfio_ccw_dev_ops = {
> +	.open_device = vfio_ccw_mdev_open_device,
> +	.close_device = vfio_ccw_mdev_close_device,
> +	.read = vfio_ccw_mdev_read,
> +	.write = vfio_ccw_mdev_write,
> +	.ioctl = vfio_ccw_mdev_ioctl,
> +	.request = vfio_ccw_mdev_request,
> +};
> +
> +struct mdev_driver vfio_ccw_mdev_driver = {
> +	.driver = {
> +		.name = "vfio_ccw_mdev",
> +		.owner = THIS_MODULE,
> +		.mod_name = KBUILD_MODNAME,
> +	},
> +	.probe = vfio_ccw_mdev_probe,
> +	.remove = vfio_ccw_mdev_remove,
> +};
> +
>  static const struct mdev_parent_ops vfio_ccw_mdev_ops = {
>  	.owner			= THIS_MODULE,
> +	.device_driver		= &vfio_ccw_mdev_driver,
>  	.supported_type_groups  = mdev_type_groups,
> -	.create			= vfio_ccw_mdev_create,
> -	.remove			= vfio_ccw_mdev_remove,
> -	.open_device		= vfio_ccw_mdev_open_device,
> -	.close_device		= vfio_ccw_mdev_close_device,
> -	.read			= vfio_ccw_mdev_read,
> -	.write			= vfio_ccw_mdev_write,
> -	.ioctl			= vfio_ccw_mdev_ioctl,
> -	.request		= vfio_ccw_mdev_request,
>  };
>  
>  int vfio_ccw_mdev_reg(struct subchannel *sch)
> diff --git a/drivers/s390/cio/vfio_ccw_private.h
> b/drivers/s390/cio/vfio_ccw_private.h
> index b2c762eb42b9bb..7272eb78861244 100644
> --- a/drivers/s390/cio/vfio_ccw_private.h
> +++ b/drivers/s390/cio/vfio_ccw_private.h
> @@ -17,6 +17,7 @@
>  #include <linux/eventfd.h>
>  #include <linux/workqueue.h>
>  #include <linux/vfio_ccw.h>
> +#include <linux/vfio.h>
>  #include <asm/crw.h>
>  #include <asm/debug.h>
>  
> @@ -67,6 +68,7 @@ struct vfio_ccw_crw {
>  
>  /**
>   * struct vfio_ccw_private
> + * @vdev: Embedded VFIO device
>   * @sch: pointer to the subchannel
>   * @state: internal state of the device
>   * @completion: synchronization helper of the I/O completion
> @@ -90,6 +92,7 @@ struct vfio_ccw_crw {
>   * @crw_work: work for deferral process of CRW handling
>   */
>  struct vfio_ccw_private {
> +	struct vfio_device vdev;
>  	struct subchannel	*sch;
>  	int			state;
>  	struct completion	*completion;
> @@ -121,6 +124,8 @@ extern void vfio_ccw_mdev_unreg(struct subchannel
> *sch);
>  
>  extern int vfio_ccw_sch_quiesce(struct subchannel *sch);
>  
> +extern struct mdev_driver vfio_ccw_mdev_driver;
> +
>  /*
>   * States of the device statemachine.
>   */