Subject: Re: [PATCH v3 1/5] mdev: Introduce sha1 based mdev alias

From: Cornelia Huck <[email-masked]>
Date: Tue, 17 Sep 2019 12:03:33 +0200

On Sun,  1 Sep 2019 23:24:32 -0500
Parav Pandit <[email-masked]> wrote:

> Some vendor drivers want an identifier for an mdev device that is
> shorter than the UUID, due to length restrictions in the consumers of
> that identifier.
> 
> Add a callback that allows a vendor driver to request an alias of a
> specified length to be generated for an mdev device. If generated,
> that alias is checked for collisions.
> 
> It is an optional attribute.
> mdev alias is generated using sha1 from the mdev name.
> 
> Signed-off-by: Parav Pandit <[email-masked]>
> 
> ---
> Changelog:
> v1->v2:
>  - Kept mdev_device naturally aligned
>  - Added error checking for crypt_*() calls
>  - Corrected a typo from 'and' to 'an'
>  - Changed return type of generate_alias() from int to char*
> v0->v1:
>  - Moved alias length check outside of the parent lock
>  - Moved alias and digest allocation from kvzalloc to kzalloc
>  - &alias[0] changed to alias
>  - alias_length check is nested under get_alias_length callback check
>  - Changed comments to start with an empty line
>  - Fixed cleaunup of hash if mdev_bus_register() fails
>  - Added comment where alias memory ownership is handed over to mdev device
>  - Updated commit log to indicate motivation for this feature
> ---
>  drivers/vfio/mdev/mdev_core.c    | 123 ++++++++++++++++++++++++++++++-
>  drivers/vfio/mdev/mdev_private.h |   5 +-
>  drivers/vfio/mdev/mdev_sysfs.c   |  13 ++--
>  include/linux/mdev.h             |   4 +
>  4 files changed, 135 insertions(+), 10 deletions(-)

(...)

> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> index 0ce30ca78db0..f036fe9854ee 100644
> --- a/include/linux/mdev.h
> +++ b/include/linux/mdev.h
> @@ -72,6 +72,9 @@ struct device *mdev_get_iommu_device(struct device *dev);
>   * @mmap:		mmap callback
>   *			@mdev: mediated device structure
>   *			@vma: vma structure
> + * @get_alias_length:	Generate alias for the mdevs of this parent based on the
> + *			mdev device name when it returns non zero alias length.

"Optional: If a non-zero alias length is returned, generate an alias
for this parent's mdevs based upon the mdev device name."

?

> + *			It is optional.
>   * Parent device that support mediated device should be registered with mdev
>   * module with mdev_parent_ops structure.
>   **/
> @@ -92,6 +95,7 @@ struct mdev_parent_ops {
>  	long	(*ioctl)(struct mdev_device *mdev, unsigned int cmd,
>  			 unsigned long arg);
>  	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
> +	unsigned int (*get_alias_length)(void);
>  };
>  
>  /* interface for exporting mdev supported type attributes */

Reviewed-by: Cornelia Huck <[email-masked]>