Date:   Wed, 18 Sep 2019 17:15:58 +0000
From:   Parav Pandit <parav@...lanox.com>
To:     Cornelia Huck <cohuck@...hat.com>
CC:     "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        Jiri Pirko <jiri@...lanox.com>,
        "kwankhede@...dia.com" <kwankhede@...dia.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH v3 0/5] Introduce variable length mdev alias

Hi Cornelia,

> -----Original Message-----
> From: Cornelia Huck <cohuck@...hat.com>
> Sent: Tuesday, September 17, 2019 5:14 AM
> To: Parav Pandit <parav@...lanox.com>
> Cc: alex.williamson@...hat.com; Jiri Pirko <jiri@...lanox.com>;
> kwankhede@...dia.com; davem@...emloft.net; kvm@...r.kernel.org; linux-
> kernel@...r.kernel.org; netdev@...r.kernel.org
> Subject: Re: [PATCH v3 0/5] Introduce variable length mdev alias
> 
> On Sun,  1 Sep 2019 23:24:31 -0500
> Parav Pandit <parav@...lanox.com> wrote:
> 
> > 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
> > 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(-)
> >
> 
> The patches on their own look sane (and I gave my R-b), but the consumer of
> this new API should be ready before this is merged, as already discussed below.

Thanks for the review. I will send v4 here to address all comments and to add your R-b tag.
I am waiting for Saeed to post other prep series of mlx5_core to be merged before I post actual consumer series, as it depends on it.
I will also drop the mtty sample patch and change-log to avoid confusion with versions when I combine them with consumer series.

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