From c3d5c2d96d69f2578d6fbf66e39cc2cf840d9812 Mon Sep 17 00:00:00 2001 From: Leon Romanovsky Date: Sun, 4 Apr 2021 10:22:18 +0300 Subject: PCI/IOV: Add sysfs MSI-X vector assignment interface A typical cloud provider SR-IOV use case is to create many VFs for use by guest VMs. The VFs may not be assigned to a VM until a customer requests a VM of a certain size, e.g., number of CPUs. A VF may need MSI-X vectors proportional to the number of CPUs in the VM, but there is no standard way to change the number of MSI-X vectors supported by a VF. Some Mellanox ConnectX devices support dynamic assignment of MSI-X vectors to SR-IOV VFs. This can be done by the PF driver after VFs are enabled, and it can be done without affecting VFs that are already in use. The hardware supports a limited pool of MSI-X vectors that can be assigned to the PF or to individual VFs. This is device-specific behavior that requires support in the PF driver. Add a read-only "sriov_vf_total_msix" sysfs file for the PF and a writable "sriov_vf_msix_count" file for each VF. Management software may use these to learn how many MSI-X vectors are available and to dynamically assign them to VFs before the VFs are passed through to a VM. If the PF driver implements the ->sriov_get_vf_total_msix() callback, "sriov_vf_total_msix" contains the total number of MSI-X vectors available for distribution among VFs. If no driver is bound to the VF, writing "N" to "sriov_vf_msix_count" uses the PF driver ->sriov_set_msix_vec_count() callback to assign "N" MSI-X vectors to the VF. When a VF driver subsequently reads the MSI-X Message Control register, it will see the new Table Size "N". Link: https://lore.kernel.org/linux-pci/20210314124256.70253-2-leon@kernel.org Acked-by: Bjorn Helgaas Signed-off-by: Leon Romanovsky --- Documentation/ABI/testing/sysfs-bus-pci | 29 +++++++++++++++++++++++++++++ 1 file changed, 29 insertions(+) (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci index 25c9c39770c6..e5cfd170b491 100644 --- a/Documentation/ABI/testing/sysfs-bus-pci +++ b/Documentation/ABI/testing/sysfs-bus-pci @@ -375,3 +375,32 @@ Description: The value comes from the PCI kernel device state and can be one of: "unknown", "error", "D0", D1", "D2", "D3hot", "D3cold". The file is read only. + +What: /sys/bus/pci/devices/.../sriov_vf_total_msix +Date: January 2021 +Contact: Leon Romanovsky +Description: + This file is associated with a SR-IOV physical function (PF). + It contains the total number of MSI-X vectors available for + assignment to all virtual functions (VFs) associated with PF. + The value will be zero if the device doesn't support this + functionality. For supported devices, the value will be + constant and won't be changed after MSI-X vectors assignment. + +What: /sys/bus/pci/devices/.../sriov_vf_msix_count +Date: January 2021 +Contact: Leon Romanovsky +Description: + This file is associated with a SR-IOV virtual function (VF). + It allows configuration of the number of MSI-X vectors for + the VF. This allows devices that have a global pool of MSI-X + vectors to optimally divide them between VFs based on VF usage. + + The values accepted are: + * > 0 - this number will be reported as the Table Size in the + VF's MSI-X capability + * < 0 - not valid + * = 0 - will reset to the device default value + + The file is writable if the PF is bound to a driver that + implements ->sriov_set_msix_vec_count(). -- cgit v1.2.3