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authorLeon Romanovsky <leonro@nvidia.com>2021-04-04 10:22:18 +0300
committerLeon Romanovsky <leonro@nvidia.com>2021-04-04 10:26:30 +0300
commitc3d5c2d96d69f2578d6fbf66e39cc2cf840d9812 (patch)
tree04d5f784853bafe12c034f35a9a013431a746217 /Documentation/ABI
parent26bf30902c10473ba38f220d3401a61c56d8db3b (diff)
downloadlinux-c3d5c2d96d69f2578d6fbf66e39cc2cf840d9812.tar.xz
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 <bhelgaas@google.com> Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-bus-pci29
1 files changed, 29 insertions, 0 deletions
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 <leonro@nvidia.com>
+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 <leonro@nvidia.com>
+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().