netdev - Re: [PATCH mlx5-next v6 1/4] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs

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Date:   Wed, 17 Feb 2021 14:28:35 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Leon Romanovsky <leon@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Saeed Mahameed <saeedm@...dia.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        Jakub Kicinski <kuba@...nel.org>, linux-pci@...r.kernel.org,
        linux-rdma@...r.kernel.org, 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>,
        Krzysztof Wilczyński <kw@...ux.com>
Subject: Re: [PATCH mlx5-next v6 1/4] PCI: Add sysfs callback to allow MSI-X
 table size change of SR-IOV VFs

On Wed, Feb 17, 2021 at 03:25:22PM -0400, Jason Gunthorpe wrote:
> On Wed, Feb 17, 2021 at 12:02:39PM -0600, Bjorn Helgaas wrote:
> 
> > > BTW, I asked more than once how these sysfs knobs should be handled
> > > in the PCI/core.
> > 
> > Thanks for the pointers.  This is the first instance I can think of
> > where we want to create PCI core sysfs files based on a driver
> > binding, so there really isn't a precedent.
> 
> The MSI stuff does it today, doesn't it? eg:
> 
> virtblk_probe (this is a driver bind)
>   init_vq
>    virtio_find_vqs
>     vp_modern_find_vqs
>      vp_find_vqs
>       vp_find_vqs_msix
>        vp_request_msix_vectors
>         pci_alloc_irq_vectors_affinity
>          __pci_enable_msi_range
>           msi_capability_init
> 	   populate_msi_sysfs
> 	    	ret = sysfs_create_groups(&pdev->dev.kobj, msi_irq_groups);
> 
> And the sysfs is removed during pci_disable_msi(), also called by the
> driver

Yes, you're right, I didn't notice that one.

I'm not quite convinced that we clean up correctly in all cases --
pci_disable_msix(), pci_disable_msi(), pci_free_irq_vectors(),
pcim_release(), etc are called by several drivers, but in my quick
look I didn't see a guaranteed-to-be-called path to the cleanup during
driver unbind.  I probably just missed it.