On Tue, Jan 26, 2021 at 10:57:27AM +0200, Leon Romanovsky wrote:

From: Leon Romanovsky <leonro@nvidia.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@nvidia.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