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Date: Sun, 31 Mar 2024 07:20:24 -0400
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
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Subject: Re: [PATCH 01/22] virtio: store owner from modules with
 register_virtio_driver()
Message-ID: <20240331071546-mutt-send-email-mst@kernel.org>
References: <20240327-module-owner-virtio-v1-0-0feffab77d99@linaro.org>
 <20240327-module-owner-virtio-v1-1-0feffab77d99@linaro.org>
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In-Reply-To: <20240327-module-owner-virtio-v1-1-0feffab77d99@linaro.org>

On Wed, Mar 27, 2024 at 01:40:54PM +0100, Krzysztof Kozlowski wrote:
> Modules registering driver with register_virtio_driver() might forget to
> set .owner field.  i2c-virtio.c for example has it missing.  The field
> is used by some of other kernel parts for reference counting
> (try_module_get()), so it is expected that drivers will set it.
> 
> Solve the problem by moving this task away from the drivers to the core
> amba bus code, just like we did for platform_driver in
> commit 9447057eaff8 ("platform_device: use a macro instead of
> platform_driver_register").
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>


This makes sense. So this will be:

Fixes: 3cfc88380413 ("i2c: virtio: add a virtio i2c frontend driver")
Cc: "Jie Deng" <jie.deng@intel.com>

and I think I will pick this patch for this cycle to fix
the bug. The cleanups can go in the next cycle.


> ---
>  Documentation/driver-api/virtio/writing_virtio_drivers.rst | 1 -
>  drivers/virtio/virtio.c                                    | 6 ++++--
>  include/linux/virtio.h                                     | 7 +++++--
>  3 files changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/Documentation/driver-api/virtio/writing_virtio_drivers.rst b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
> index e14c58796d25..e5de6f5d061a 100644
> --- a/Documentation/driver-api/virtio/writing_virtio_drivers.rst
> +++ b/Documentation/driver-api/virtio/writing_virtio_drivers.rst
> @@ -97,7 +97,6 @@ like this::
>  
>  	static struct virtio_driver virtio_dummy_driver = {
>  		.driver.name =  KBUILD_MODNAME,
> -		.driver.owner = THIS_MODULE,
>  		.id_table =     id_table,
>  		.probe =        virtio_dummy_probe,
>  		.remove =       virtio_dummy_remove,
> diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> index f173587893cb..9510c551dce8 100644
> --- a/drivers/virtio/virtio.c
> +++ b/drivers/virtio/virtio.c
> @@ -362,14 +362,16 @@ static const struct bus_type virtio_bus = {
>  	.remove = virtio_dev_remove,
>  };
>  
> -int register_virtio_driver(struct virtio_driver *driver)
> +int __register_virtio_driver(struct virtio_driver *driver, struct module *owner)
>  {
>  	/* Catch this early. */
>  	BUG_ON(driver->feature_table_size && !driver->feature_table);
>  	driver->driver.bus = &virtio_bus;
> +	driver->driver.owner = owner;
> +
>  	return driver_register(&driver->driver);
>  }
> -EXPORT_SYMBOL_GPL(register_virtio_driver);
> +EXPORT_SYMBOL_GPL(__register_virtio_driver);
>  
>  void unregister_virtio_driver(struct virtio_driver *driver)
>  {
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index b0201747a263..26c4325aa373 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -170,7 +170,7 @@ size_t virtio_max_dma_size(const struct virtio_device *vdev);
>  
>  /**
>   * struct virtio_driver - operations for a virtio I/O driver
> - * @driver: underlying device driver (populate name and owner).
> + * @driver: underlying device driver (populate name).
>   * @id_table: the ids serviced by this driver.
>   * @feature_table: an array of feature numbers supported by this driver.
>   * @feature_table_size: number of entries in the feature table array.
> @@ -208,7 +208,10 @@ static inline struct virtio_driver *drv_to_virtio(struct device_driver *drv)
>  	return container_of(drv, struct virtio_driver, driver);
>  }
>  
> -int register_virtio_driver(struct virtio_driver *drv);
> +/* use a macro to avoid include chaining to get THIS_MODULE */
> +#define register_virtio_driver(drv) \
> +	__register_virtio_driver(drv, THIS_MODULE)
> +int __register_virtio_driver(struct virtio_driver *drv, struct module *owner);
>  void unregister_virtio_driver(struct virtio_driver *drv);
>  
>  /* module_virtio_driver() - Helper macro for drivers that don't do
> 
> -- 
> 2.34.1