netdev - Re: [PATCH mlx5-next v5 1/4] PCI: Add sysfs callback to allow MSI-X table size change of SR-IOV VFs

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Date:   Tue, 2 Feb 2021 09:02:46 +0200
From:   Leon Romanovsky <leonro@...dia.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Saeed Mahameed <saeedm@...dia.com>
CC:     Jason Gunthorpe <jgg@...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>
Subject: Re: [PATCH mlx5-next v5 1/4] PCI: Add sysfs callback to allow MSI-X
 table size change of SR-IOV VFs

On Tue, Jan 26, 2021 at 10:57:27AM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
>
> Extend PCI sysfs interface with a new callback that allows configure
> the number of MSI-X vectors for specific SR-IO VF. This is needed
> to optimize the performance of newly bound devices by allocating
> the number of vectors based on the administrator knowledge of targeted VM.
>
> This function is applicable for SR-IOV VF because such devices allocate
> their MSI-X table before they will run on the VMs and HW can't guess the
> right number of vectors, so the HW allocates them statically and equally.
>
> 1) The newly added /sys/bus/pci/devices/.../vfs_overlay/sriov_vf_msix_count
> file will be seen for the VFs and it is writable as long as a driver is not
> bounded to the VF.
>
> The values accepted are:
>  * > 0 - this will be number reported by the VF's MSI-X capability
>  * < 0 - not valid
>  * = 0 - will reset to the device default value
>
> 2) In order to make management easy, provide new read-only sysfs file that
> returns a total number of possible to configure MSI-X vectors.
>
> cat /sys/bus/pci/devices/.../vfs_overlay/sriov_vf_total_msix
>   = 0 - feature is not supported
>   > 0 - total number of MSI-X vectors to consume by the VFs
>
> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> ---
>  Documentation/ABI/testing/sysfs-bus-pci |  32 +++++
>  drivers/pci/iov.c                       | 180 ++++++++++++++++++++++++
>  drivers/pci/msi.c                       |  47 +++++++
>  drivers/pci/pci.h                       |   4 +
>  include/linux/pci.h                     |  10 ++
>  5 files changed, 273 insertions(+)

Bjorn,

Can I please get your Acked-by on this so it will go through
mlx5-next -> netdev submission flow?

Thanks