Re: [Intel-gfx] [PATCH v3 07/14] vfio/platform: Use open_device() instead of open coding a refcnt scheme

[Eric Auger <eric.auger@redhat.com>]

Hi Jason,

On 7/29/21 2:49 AM, Jason Gunthorpe wrote:
> Platform simply wants to run some code when the device is first
> opened/last closed. Use the core framework and locking for this.  Aside
> from removing a bit of code this narrows the locking scope from a global
> lock.
>
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> Signed-off-by: Yishai Hadas <yishaih@nvidia.com>
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> ---
>  drivers/vfio/platform/vfio_platform_common.c  | 79 ++++++++-----------
>  drivers/vfio/platform/vfio_platform_private.h |  1 -
>  2 files changed, 32 insertions(+), 48 deletions(-)
>
> diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
> index bdde8605178cd2..6af7ce7d619c25 100644
> --- a/drivers/vfio/platform/vfio_platform_common.c
> +++ b/drivers/vfio/platform/vfio_platform_common.c
> @@ -218,65 +218,52 @@ static int vfio_platform_call_reset(struct vfio_platform_device *vdev,
>  	return -EINVAL;
>  }
>  
> -static void vfio_platform_release(struct vfio_device *core_vdev)
> +static void vfio_platform_close_device(struct vfio_device *core_vdev)
>  {
>  	struct vfio_platform_device *vdev =
>  		container_of(core_vdev, struct vfio_platform_device, vdev);
> +	const char *extra_dbg = NULL;
> +	int ret;
>  
> -	mutex_lock(&driver_lock);
> -
> -	if (!(--vdev->refcnt)) {
> -		const char *extra_dbg = NULL;
> -		int ret;
> -
> -		ret = vfio_platform_call_reset(vdev, &extra_dbg);
> -		if (ret && vdev->reset_required) {
> -			dev_warn(vdev->device, "reset driver is required and reset call failed in release (%d) %s\n",
> -				 ret, extra_dbg ? extra_dbg : "");
> -			WARN_ON(1);
> -		}
> -		pm_runtime_put(vdev->device);
> -		vfio_platform_regions_cleanup(vdev);
> -		vfio_platform_irq_cleanup(vdev);
> +	ret = vfio_platform_call_reset(vdev, &extra_dbg);
> +	if (WARN_ON(ret && vdev->reset_required)) {
> +		dev_warn(
> +			vdev->device,
> +			"reset driver is required and reset call failed in release (%d) %s\n",
> +			ret, extra_dbg ? extra_dbg : "");
>  	}
> -
> -	mutex_unlock(&driver_lock);
> +	pm_runtime_put(vdev->device);
> +	vfio_platform_regions_cleanup(vdev);
> +	vfio_platform_irq_cleanup(vdev);
>  }
>  
> -static int vfio_platform_open(struct vfio_device *core_vdev)
> +static int vfio_platform_open_device(struct vfio_device *core_vdev)
>  {
>  	struct vfio_platform_device *vdev =
>  		container_of(core_vdev, struct vfio_platform_device, vdev);
> +	const char *extra_dbg = NULL;
>  	int ret;
>  
> -	mutex_lock(&driver_lock);
> -
> -	if (!vdev->refcnt) {
> -		const char *extra_dbg = NULL;
> -
> -		ret = vfio_platform_regions_init(vdev);
> -		if (ret)
> -			goto err_reg;
> +	ret = vfio_platform_regions_init(vdev);
> +	if (ret)
> +		return ret;
>  
> -		ret = vfio_platform_irq_init(vdev);
> -		if (ret)
> -			goto err_irq;
> +	ret = vfio_platform_irq_init(vdev);
> +	if (ret)
> +		goto err_irq;
>  
> -		ret = pm_runtime_get_sync(vdev->device);
> -		if (ret < 0)
> -			goto err_rst;
> +	ret = pm_runtime_get_sync(vdev->device);
> +	if (ret < 0)
> +		goto err_rst;
>  
> -		ret = vfio_platform_call_reset(vdev, &extra_dbg);
> -		if (ret && vdev->reset_required) {
> -			dev_warn(vdev->device, "reset driver is required and reset call failed in open (%d) %s\n",
> -				 ret, extra_dbg ? extra_dbg : "");
> -			goto err_rst;
> -		}
> +	ret = vfio_platform_call_reset(vdev, &extra_dbg);
> +	if (ret && vdev->reset_required) {
> +		dev_warn(
> +			vdev->device,
> +			"reset driver is required and reset call failed in open (%d) %s\n",
> +			ret, extra_dbg ? extra_dbg : "");
> +		goto err_rst;
>  	}
> -
> -	vdev->refcnt++;
> -
> -	mutex_unlock(&driver_lock);
>  	return 0;
>  
>  err_rst:
> @@ -284,8 +271,6 @@ static int vfio_platform_open(struct vfio_device *core_vdev)
>  	vfio_platform_irq_cleanup(vdev);
>  err_irq:
>  	vfio_platform_regions_cleanup(vdev);
> -err_reg:
> -	mutex_unlock(&driver_lock);
>  	return ret;
>  }
>  
> @@ -616,8 +601,8 @@ static int vfio_platform_mmap(struct vfio_device *core_vdev, struct vm_area_stru
>  
>  static const struct vfio_device_ops vfio_platform_ops = {
>  	.name		= "vfio-platform",
> -	.open		= vfio_platform_open,
> -	.release	= vfio_platform_release,
> +	.open_device	= vfio_platform_open_device,
> +	.close_device	= vfio_platform_close_device,
>  	.ioctl		= vfio_platform_ioctl,
>  	.read		= vfio_platform_read,
>  	.write		= vfio_platform_write,
> diff --git a/drivers/vfio/platform/vfio_platform_private.h b/drivers/vfio/platform/vfio_platform_private.h
> index dfb834c1365946..520d2a8e8375b2 100644
> --- a/drivers/vfio/platform/vfio_platform_private.h
> +++ b/drivers/vfio/platform/vfio_platform_private.h
> @@ -48,7 +48,6 @@ struct vfio_platform_device {
>  	u32				num_regions;
>  	struct vfio_platform_irq	*irqs;
>  	u32				num_irqs;
> -	int				refcnt;
>  	struct mutex			igate;
>  	const char			*compat;
>  	const char			*acpihid;