netdev - Re: [PATCH mlx5-next v7 0/4] Dynamically assign MSI-X vectors count

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Message-ID: <YEptn6d9fD4q2b52@unreal>
Date:   Thu, 11 Mar 2021 21:21:03 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Keith Busch <kbusch@...nel.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Jakub Kicinski <kuba@...nel.org>,
        linux-pci <linux-pci@...r.kernel.org>,
        linux-rdma@...r.kernel.org, Netdev <netdev@...r.kernel.org>,
        Don Dutile <ddutile@...hat.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        "David S . Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH mlx5-next v7 0/4] Dynamically assign MSI-X vectors count

On Thu, Mar 11, 2021 at 12:16:02PM -0700, Keith Busch wrote:
> On Thu, Mar 11, 2021 at 12:17:29PM -0600, Bjorn Helgaas wrote:
> > On Wed, Mar 10, 2021 at 03:34:01PM -0800, Alexander Duyck wrote:
> > >
> > > I'm not so much worried about management software as the fact that
> > > this is a vendor specific implementation detail that is shaping how
> > > the kernel interfaces are meant to work. Other than the mlx5 I don't
> > > know if there are any other vendors really onboard with this sort of
> > > solution.
> >
> > I know this is currently vendor-specific, but I thought the value
> > proposition of dynamic configuration of VFs for different clients
> > sounded compelling enough that other vendors would do something
> > similar.  But I'm not an SR-IOV guy and have no vendor insight, so
> > maybe that's not the case?
>
> NVMe has a similar feature defined by the standard where a PF controller can
> dynamically assign MSIx vectors to VFs. The whole thing is managed in user
> space with an ioctl, though. I guess we could wire up the driver to handle it
> through this sysfs interface too, but I think the protocol specific tooling is
> more appropriate for nvme.

We need this MSI-X thing for IB and ethernet devices too. This is why PCI
sysfs is the best place to put it, so all SR-IOV flavours will have sane
way to configure it.

Thanks