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From:   Parav Pandit <parav@mellanox.com>
To:     Alex Williamson <alex.williamson@redhat.com>
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Subject: RE: [PATCH v3 0/5] Introduce variable length mdev alias
Thread-Topic: [PATCH v3 0/5] Introduce variable length mdev alias
Thread-Index: AQHVYUZdAS6KYIr8SUO1vQ8myuXcNacjy68wgALDGQCAABfpQA==
Date:   Wed, 11 Sep 2019 15:30:40 +0000
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Hi Alex,

> -----Original Message-----
> From: Alex Williamson <alex.williamson@redhat.com>
> Sent: Wednesday, September 11, 2019 8:56 AM
> To: Parav Pandit <parav@mellanox.com>
> Cc: Jiri Pirko <jiri@mellanox.com>; kwankhede@nvidia.com;
> cohuck@redhat.com; davem@davemloft.net; kvm@vger.kernel.org; linux-
> kernel@vger.kernel.org; netdev@vger.kernel.org
> Subject: Re: [PATCH v3 0/5] Introduce variable length mdev alias
>=20
> On Mon, 9 Sep 2019 20:42:32 +0000
> Parav Pandit <parav@mellanox.com> wrote:
>=20
> > 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=3D83b8f4f2-509f-382f-3c1e-e6bfe0fa1001
> > > mdev 12 character alias=3Dcd5b146a80a5
> > >
> > > netdev name of this mdev =3D enmcd5b146a80a5 Here en =3D Ethernet lin=
k m
> > > =3D mediated device
> > >
> > > 2. devlink port phys_port_name created using mdev alias.
> > > devlink phys_port_name=3Dpcd5b146a80a5
> > >
> > > 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() =3D=3D0 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.
>=20
> Sorry, I'm at LPC this week.  I agree, I don't think the double allocatio=
n is
> necessary, I thought the comment was sufficient to clarify null'ing the
> variable.  It's awkward, but seems correct.
>=20
> I'm not sure what we do with this patch series though, has the real
> consumer of this even been proposed?  It feels optimistic to include at t=
his
> point.  We've used the sample driver as a placeholder in the past for
> mdev_uuid(), but we arrived at that via a conversion rather than explicit=
ly
> adding the API.  Please let me know where the consumer patches stand,
> perhaps it would make more sense for them to go in together rather than
> risk adding an unused API.  Thanks,
>=20
Given that consumer patch series is relatively large (around 15+ patches), =
I was considering to merge this one as pre-series to it.
Its ok to combine this with consumer patch series.
But wanted to have it reviewed beforehand, so that churn is less in actual =
consumer series which is more mlx5_core and devlink/netdev centric.
So if you can add Review-by, it will be easier to combine with consumer ser=
ies.

And if we merge it with consumer series, it will come through Dave Miller's=
 tree instead of your tree.
Would that work for you?