linux-kernel - RE: [PATCH v3 0/2] vdpa: support set mac address from vdpa tool

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Message-ID:
 <PH0PR12MB54819872A2A265285EF097A7DCA42@PH0PR12MB5481.namprd12.prod.outlook.com>
Date: Wed, 10 Jul 2024 03:44:06 +0000
From: Parav Pandit <parav@...dia.com>
To: Jason Wang <jasowang@...hat.com>, "Michael S. Tsirkin" <mst@...hat.com>
CC: Cindy Lu <lulu@...hat.com>, Dragos Tatulea <dtatulea@...dia.com>,
	"sgarzare@...hat.com" <sgarzare@...hat.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, "virtualization@...ts.linux-foundation.org"
	<virtualization@...ts.linux-foundation.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	Leonardo Milleri <lmilleri@...hat.com>
Subject: RE: [PATCH v3 0/2] vdpa: support set mac address from vdpa tool

Hi Cindy,

> From: Jason Wang <jasowang@...hat.com>
> Sent: Wednesday, July 10, 2024 8:36 AM
> 
> On Tue, Jul 9, 2024 at 8:42 PM Michael S. Tsirkin <mst@...hat.com> wrote:
> >
> > On Tue, Jul 09, 2024 at 02:19:19PM +0800, Cindy Lu wrote:
> > > On Tue, 9 Jul 2024 at 11:59, Parav Pandit <parav@...dia.com> wrote:
> > > >
> > > > Hi Cindy,
> > > >
> > > > > From: Cindy Lu <lulu@...hat.com>
> > > > > Sent: Monday, July 8, 2024 12:17 PM
> > > > >
> > > > > Add support for setting the MAC address using the VDPA tool.
> > > > > This feature will allow setting the MAC address using the VDPA tool.
> > > > > For example, in vdpa_sim_net, the implementation sets the MAC
> > > > > address to the config space. However, for other drivers, they
> > > > > can implement their own function, not limited to the config space.
> > > > >
> > > > > Changelog v2
> > > > >  - Changed the function name to prevent misunderstanding
> > > > >  - Added check for blk device
> > > > >  - Addressed the comments
> > > > > Changelog v3
> > > > >  - Split the function of the net device from
> > > > > vdpa_nl_cmd_dev_attr_set_doit
> > > > >  - Add a lock for the network device's dev_set_attr operation
> > > > >  - Address the comments
> > > > >
> > > > > Cindy Lu (2):
> > > > >   vdpa: support set mac address from vdpa tool
> > > > >   vdpa_sim_net: Add the support of set mac address
> > > > >
> > > > >  drivers/vdpa/vdpa.c                  | 81 ++++++++++++++++++++++++++++
> > > > >  drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 19 ++++++-
> > > > >  include/linux/vdpa.h                 |  9 ++++
> > > > >  include/uapi/linux/vdpa.h            |  1 +
> > > > >  4 files changed, 109 insertions(+), 1 deletion(-)
> > > > >
> > > > > --
> > > > > 2.45.0
> > > >
> > > > Mlx5 device already allows setting the mac and mtu during the vdpa
> device creation time.
> > > > Once the vdpa device is created, it binds to vdpa bus and other driver
> vhost_vdpa etc bind to it.
> > > > So there was no good reason in the past to support explicit config after
> device add complicate the flow for synchronizing this.
> > > >
> > > > The user who wants a device with new attributes, as well destroy and
> recreate the vdpa device with new desired attributes.
> > > >
> > > > vdpa_sim_net can also be extended for similar way when adding the
> vdpa device.
> > > >
> > > > Have you considered using the existing tool and kernel in place since
> 2021?
> > > > Such as commit d8ca2fa5be1.
> > > >
> > > > An example of it is,
> > > > $ vdpa dev add name bar mgmtdev vdpasim_net mac 00:11:22:33:44:55
> > > > mtu 9000
> > > >
> > > Hi Parav
> > > Really thanks for your comments. The reason for adding this function
> > > is to support Kubevirt.
> > > the problem we meet is that kubevirt chooses one random vdpa device
> > > from the pool and we don't know which one it going to pick. That
> > > means we can't get to know the Mac address before it is created. So
> > > we plan to have this function to change the mac address after it is
> > > created Thanks cindy
> >
> > Well you will need to change kubevirt to teach it to set mac address,
> > right?
> 
> That's the plan. Adding Leonardo.

Any specific reason to pre-create those large number of vdpa devices of the pool?
I was hoping to create vdpa device with needed attributes, when spawning a kubevirt instance.
K8s DRA infrastructure [1] can be used to create the needed vdpa device. Have you considered using the DRA of [1]?

[1] https://kubernetes.io/docs/concepts/scheduling-eviction/dynamic-resource-allocation/