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Message-ID: <9fe1e000-e3ff-bf42-28f7-169fb57dc1ce@linux.ibm.com>
Date:   Mon, 5 Dec 2022 14:20:53 -0500
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Subject: Re: [PATCH] vfio/ap/ccw/samples: Fix device_register() unwind path
Content-Language: en-US
To:     Alex Williamson <alex.williamson@redhat.com>
Cc:     ruanjinjie <ruanjinjie@huawei.com>,
        Halil Pasic <pasic@linux.ibm.com>,
        Jason Herne <jjherne@linux.ibm.com>,
        Kirti Wankhede <kwankhede@nvidia.com>,
        Kevin Tian <kevin.tian@intel.com>,
        Eric Farman <farman@linux.ibm.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <166999942139.645727.12439756512449846442.stgit@omen>
From:   Anthony Krowiak <akrowiak@linux.ibm.com>
In-Reply-To: <166999942139.645727.12439756512449846442.stgit@omen>
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Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>

On 12/2/22 11:46 AM, Alex Williamson wrote:
> We always need to call put_device() if device_register() fails.
> All vfio drivers calling device_register() include a similar unwind
> stack via gotos, therefore split device_unregister() into its
> device_del() and put_device() components in the unwind path, and
> add a goto target to handle only the put_device() requirement.
>
> Reported-by: Ruan Jinjie <ruanjinjie@huawei.com>
> Link: https://lore.kernel.org/all/20221118032827.3725190-1-ruanjinjie@huawei.com
> Fixes: d61fc96f47fd ("sample: vfio mdev display - host device")
> Fixes: 9d1a546c53b4 ("docs: Sample driver to demonstrate how to use Mediated device framework.")
> Fixes: a5e6e6505f38 ("sample: vfio bochs vbe display (host device for bochs-drm)")
> Fixes: 9e6f07cd1eaa ("vfio/ccw: create a parent struct")
> Fixes: 36360658eb5a ("s390: vfio_ap: link the vfio_ap devices to the vfio_ap bus subsystem")
> Cc: Tony Krowiak <akrowiak@linux.ibm.com>
> Cc: Halil Pasic <pasic@linux.ibm.com>
> Cc: Jason Herne <jjherne@linux.ibm.com>
> Cc: Kirti Wankhede <kwankhede@nvidia.com>
> Reviewed-by: Kevin Tian <kevin.tian@intel.com>
> Reviewed-by: Eric Farman <farman@linux.ibm.com>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>
> I didn't intend to usurp Ruan's patch, but since the inline version is
> collecting reviews, formally post it and include additional fixes tags
> for vfio-ccw and vfio-ap.
>
>   drivers/s390/cio/vfio_ccw_drv.c   |    3 ++-
>   drivers/s390/crypto/vfio_ap_drv.c |    2 +-
>   samples/vfio-mdev/mbochs.c        |    7 ++++---
>   samples/vfio-mdev/mdpy.c          |    7 ++++---
>   samples/vfio-mdev/mtty.c          |    7 ++++---
>   5 files changed, 15 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c
> index c2a65808605a..54aba7cceb33 100644
> --- a/drivers/s390/cio/vfio_ccw_drv.c
> +++ b/drivers/s390/cio/vfio_ccw_drv.c
> @@ -199,8 +199,9 @@ static int vfio_ccw_sch_probe(struct subchannel *sch)
>   	return 0;
>   
>   out_unreg:
> -	device_unregister(&parent->dev);
> +	device_del(&parent->dev);
>   out_free:
> +	put_device(&parent->dev);
>   	dev_set_drvdata(&sch->dev, NULL);
>   	return ret;
>   }
> diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
> index f43cfeabd2cc..997b524bdd2b 100644
> --- a/drivers/s390/crypto/vfio_ap_drv.c
> +++ b/drivers/s390/crypto/vfio_ap_drv.c
> @@ -122,7 +122,7 @@ static int vfio_ap_matrix_dev_create(void)
>   	return 0;
>   
>   matrix_drv_err:
> -	device_unregister(&matrix_dev->device);
> +	device_del(&matrix_dev->device);
>   matrix_reg_err:
>   	put_device(&matrix_dev->device);
>   matrix_alloc_err:
> diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
> index 8b5a3a778a25..e54eb752e1ba 100644
> --- a/samples/vfio-mdev/mbochs.c
> +++ b/samples/vfio-mdev/mbochs.c
> @@ -1430,7 +1430,7 @@ static int __init mbochs_dev_init(void)
>   
>   	ret = device_register(&mbochs_dev);
>   	if (ret)
> -		goto err_class;
> +		goto err_put;
>   
>   	ret = mdev_register_parent(&mbochs_parent, &mbochs_dev, &mbochs_driver,
>   				   mbochs_mdev_types,
> @@ -1441,8 +1441,9 @@ static int __init mbochs_dev_init(void)
>   	return 0;
>   
>   err_device:
> -	device_unregister(&mbochs_dev);
> -err_class:
> +	device_del(&mbochs_dev);
> +err_put:
> +	put_device(&mbochs_dev);
>   	class_destroy(mbochs_class);
>   err_driver:
>   	mdev_unregister_driver(&mbochs_driver);
> diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
> index 721fb06c6413..e8400fdab71d 100644
> --- a/samples/vfio-mdev/mdpy.c
> +++ b/samples/vfio-mdev/mdpy.c
> @@ -717,7 +717,7 @@ static int __init mdpy_dev_init(void)
>   
>   	ret = device_register(&mdpy_dev);
>   	if (ret)
> -		goto err_class;
> +		goto err_put;
>   
>   	ret = mdev_register_parent(&mdpy_parent, &mdpy_dev, &mdpy_driver,
>   				   mdpy_mdev_types,
> @@ -728,8 +728,9 @@ static int __init mdpy_dev_init(void)
>   	return 0;
>   
>   err_device:
> -	device_unregister(&mdpy_dev);
> -err_class:
> +	device_del(&mdpy_dev);
> +err_put:
> +	put_device(&mdpy_dev);
>   	class_destroy(mdpy_class);
>   err_driver:
>   	mdev_unregister_driver(&mdpy_driver);
> diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
> index 3c2a421b9b69..e887de672c52 100644
> --- a/samples/vfio-mdev/mtty.c
> +++ b/samples/vfio-mdev/mtty.c
> @@ -1330,7 +1330,7 @@ static int __init mtty_dev_init(void)
>   
>   	ret = device_register(&mtty_dev.dev);
>   	if (ret)
> -		goto err_class;
> +		goto err_put;
>   
>   	ret = mdev_register_parent(&mtty_dev.parent, &mtty_dev.dev,
>   				   &mtty_driver, mtty_mdev_types,
> @@ -1340,8 +1340,9 @@ static int __init mtty_dev_init(void)
>   	return 0;
>   
>   err_device:
> -	device_unregister(&mtty_dev.dev);
> -err_class:
> +	device_del(&mtty_dev.dev);
> +err_put:
> +	put_device(&mtty_dev.dev);
>   	class_destroy(mtty_dev.vd_class);
>   err_driver:
>   	mdev_unregister_driver(&mtty_driver);
>
>