RE: [PATCH v3 0/5] Introduce variable length mdev alias

Parav Pandit
2019-09-09T20:42:42Z

Hi Alex,

> -----Original Message-----
> From: Parav Pandit <parav@mellanox.com>
> Sent: Sunday, September 1, 2019 11:25 PM
> To: alex.williamson@redhat.com; Jiri Pirko <jiri@mellanox.com>;
> kwankhede@nvidia.com; cohuck@redhat.com; davem@davemloft.net
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org;
> netdev@vger.kernel.org; Parav Pandit <parav@mellanox.com>
> Subject: [PATCH v3 0/5] Introduce variable length mdev alias
>
> To have consistent naming for the netdevice of a mdev and to have consistent
> naming of the devlink port [1] of a mdev, which is formed using
> phys_port_name of the devlink port, current UUID is not usable because UUID
> is too long.
>
> UUID in string format is 36-characters long and in binary 128-bit.
> Both formats are not able to fit within 15 characters limit of netdev name.
>
> It is desired to have mdev device naming consistent using UUID.
> So that widely used user space framework such as ovs [2] can make use of
> mdev representor in similar way as PCIe SR-IOV VF and PF representors.
>
> Hence,
> (a) mdev alias is created which is derived using sha1 from the mdev name.
> (b) Vendor driver describes how long an alias should be for the child mdev
> created for a given parent.
> (c) Mdev aliases are unique at system level.
> (d) alias is created optionally whenever parent requested.
> This ensures that non networking mdev parents can function without alias
> creation overhead.
>
> This design is discussed at [3].
>
> An example systemd/udev extension will have,
>
> 1. netdev name created using mdev alias available in sysfs.
>
> mdev UUID=83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
> mdev 12 character alias=cd5b146a80a5
>
> netdev name of this mdev = enmcd5b146a80a5 Here en = Ethernet link m =
> mediated device
>
> 2. devlink port phys_port_name created using mdev alias.
> devlink phys_port_name=pcd5b146a80a5
>
> This patchset enables mdev core to maintain unique alias for a mdev.
>
> Patch-1 Introduces mdev alias using sha1.
> Patch-2 Ensures that mdev alias is unique in a system.
> Patch-3 Exposes mdev alias in a sysfs hirerchy, update Documentation
> Patch-4 Introduces mdev_alias() API.
> Patch-5 Extends mtty driver to optionally provide alias generation.
> This also enables to test UUID based sha1 collision and trigger error handling
> for duplicate sha1 results.
>
> [1] http://man7.org/linux/man-pages/man8/devlink-port.8.html
> [2] https://docs.openstack.org/os-vif/latest/user/plugins/ovs.html
> [3] https://patchwork.kernel.org/cover/11084231/
>
> ---
> Changelog:
> v2->v3:
> - Addressed comment from Yunsheng Lin
> - Changed strcmp() ==0 to !strcmp()
> - Addressed comment from Cornelia Hunk
> - Merged sysfs Documentation patch with syfs patch
> - Added more description for alias return value

Did you get a chance review this updated series?
I addressed Cornelia's and yours comment.
I do not think allocating alias memory twice, once for comparison and once for storing is good idea or moving alias generation logic inside the mdev_list_lock(). So I didn't address that suggestion of Cornelia.

> v1->v2:
> - Corrected a typo from 'and' to 'an'
> - Addressed comments from Alex Williamson
> - Kept mdev_device naturally aligned
> - Added error checking for crypt_*() calls
> - Moved alias NULL check at beginning
> - Added mdev_alias() API
> - Updated mtty driver to show example mdev_alias() usage
> - Changed return type of generate_alias() from int to char*
> v0->v1:
> - Addressed comments from Alex Williamson, Cornelia Hunk and Mark Bloch
> - 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
> - Added comment where alias memory ownership is handed over to mdev
> device
> - Fixed cleaunup of hash if mdev_bus_register() fails
> - Updated documentation for new sysfs alias file
> - Improved commit logs to make description more clear
> - Fixed inclusiong of alias for NULL check
> - Added ratelimited debug print for sha1 hash collision error
>
> Parav Pandit (5):
> mdev: Introduce sha1 based mdev alias
> mdev: Make mdev alias unique among all mdevs
> mdev: Expose mdev alias in sysfs tree
> mdev: Introduce an API mdev_alias
> mtty: Optionally support mtty alias
>
> .../driver-api/vfio-mediated-device.rst | 9 ++
> drivers/vfio/mdev/mdev_core.c | 142 +++++++++++++++++-
> drivers/vfio/mdev/mdev_private.h | 5 +-
> drivers/vfio/mdev/mdev_sysfs.c | 26 +++-
> include/linux/mdev.h | 5 +
> samples/vfio-mdev/mtty.c | 13 ++
> 6 files changed, 190 insertions(+), 10 deletions(-)
>
> --
> 2.19.2