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[mlx5-next,0/4] Dynamically assign MSI-X vectors count

Message ID 20210103082440.34994-1-leon@kernel.org
Headers show
Series Dynamically assign MSI-X vectors count | expand

Message

Leon Romanovsky Jan. 3, 2021, 8:24 a.m. UTC
From: Leon Romanovsky <leonro@nvidia.com>

Hi,

The number of MSI-X vectors is PCI property visible through lspci, that
field is read-only and configured by the device.

The static assignment of an amount of MSI-X vectors doesn't allow utilize
the newly created VF because it is not known to the device the future load
and configuration where that VF will be used.

The VFs are created on the hypervisor and forwarded to the VMs that have
different properties (for example number of CPUs).

To overcome the inefficiency in the spread of such MSI-X vectors, we
allow the kernel to instruct the device with the needed number of such
vectors, before VF is initialized and bounded to the driver.

Before this series:
[root@server ~]# lspci -vs 0000:08:00.2
08:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
....
	Capabilities: [9c] MSI-X: Enable- Count=12 Masked-

Configuration script:
1. Start fresh
echo 0 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_numvfs
modprobe -q -r mlx5_ib mlx5_core
2. Ensure that driver doesn't run and it is safe to change MSI-X
echo 0 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_drivers_autoprobe
3. Load driver for the PF
modprobe mlx5_core
4. Configure one of the VFs with new number
echo 2 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_numvfs
echo 21 > /sys/bus/pci/devices/0000\:08\:00.2/vf_msix_vec

After this series:
[root@server ~]# lspci -vs 0000:08:00.2
08:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
....
	Capabilities: [9c] MSI-X: Enable- Count=21 Masked-


Thanks

Leon Romanovsky (4):
  PCI: Configure number of MSI-X vectors for SR-IOV VFs
  net/mlx5: Add dynamic MSI-X capabilities bits
  net/mlx5: Dynamically assign MSI-X vectors count
  net/mlx5: Allow to the users to configure number of MSI-X vectors

 Documentation/ABI/testing/sysfs-bus-pci       | 16 +++++
 .../net/ethernet/mellanox/mlx5/core/main.c    |  5 ++
 .../ethernet/mellanox/mlx5/core/mlx5_core.h   |  6 ++
 .../net/ethernet/mellanox/mlx5/core/pci_irq.c | 62 +++++++++++++++++++
 .../net/ethernet/mellanox/mlx5/core/sriov.c   | 49 ++++++++++++++-
 drivers/pci/iov.c                             | 57 +++++++++++++++++
 drivers/pci/msi.c                             | 30 +++++++++
 drivers/pci/pci-sysfs.c                       |  1 +
 drivers/pci/pci.h                             |  1 +
 include/linux/mlx5/mlx5_ifc.h                 | 11 +++-
 include/linux/pci.h                           |  8 +++
 11 files changed, 243 insertions(+), 3 deletions(-)

--
2.29.2

Comments

Leon Romanovsky Jan. 6, 2021, 5:50 a.m. UTC | #1
On Sun, Jan 03, 2021 at 10:24:36AM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@nvidia.com>
>
> Hi,
>
> The number of MSI-X vectors is PCI property visible through lspci, that
> field is read-only and configured by the device.
>
> The static assignment of an amount of MSI-X vectors doesn't allow utilize
> the newly created VF because it is not known to the device the future load
> and configuration where that VF will be used.
>
> The VFs are created on the hypervisor and forwarded to the VMs that have
> different properties (for example number of CPUs).
>
> To overcome the inefficiency in the spread of such MSI-X vectors, we
> allow the kernel to instruct the device with the needed number of such
> vectors, before VF is initialized and bounded to the driver.
>
> Before this series:
> [root@server ~]# lspci -vs 0000:08:00.2
> 08:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
> ....
> 	Capabilities: [9c] MSI-X: Enable- Count=12 Masked-
>
> Configuration script:
> 1. Start fresh
> echo 0 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_numvfs
> modprobe -q -r mlx5_ib mlx5_core
> 2. Ensure that driver doesn't run and it is safe to change MSI-X
> echo 0 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_drivers_autoprobe
> 3. Load driver for the PF
> modprobe mlx5_core
> 4. Configure one of the VFs with new number
> echo 2 > /sys/bus/pci/devices/0000\:08\:00.0/sriov_numvfs
> echo 21 > /sys/bus/pci/devices/0000\:08\:00.2/vf_msix_vec
>
> After this series:
> [root@server ~]# lspci -vs 0000:08:00.2
> 08:00.2 Ethernet controller: Mellanox Technologies MT27800 Family [ConnectX-5 Virtual Function]
> ....
> 	Capabilities: [9c] MSI-X: Enable- Count=21 Masked-
>
>
> Thanks
>
> Leon Romanovsky (4):
>   PCI: Configure number of MSI-X vectors for SR-IOV VFs
>   net/mlx5: Add dynamic MSI-X capabilities bits
>   net/mlx5: Dynamically assign MSI-X vectors count
>   net/mlx5: Allow to the users to configure number of MSI-X vectors

Hi Bjorn,

I would like to route the PCI patch through mlx5-next tree which will
be taken to the netdev and rdma trees.

This is needed to avoid any possible merge conflicts between three
subsystems PCI, netdev and RDMA.

Is it acceptable by you?

Thanks