PCI: SRIOV control and status via sysfs (documentation)
Add documentation of new sysfs files and new pci_driver SRIOV configuration interface. [bhelgaas: changelog] Signed-off: Donald Dutile <ddutile@redhat.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
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@ -222,3 +222,37 @@ Description:
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satisfied too. Reading this attribute will show the current
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satisfied too. Reading this attribute will show the current
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value of d3cold_allowed bit. Writing this attribute will set
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value of d3cold_allowed bit. Writing this attribute will set
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the value of d3cold_allowed bit.
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the value of d3cold_allowed bit.
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What: /sys/bus/pci/devices/.../sriov_totalvfs
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Date: November 2012
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Contact: Donald Dutile <ddutile@redhat.com>
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Description:
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This file appears when a physical PCIe device supports SR-IOV.
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Userspace applications can read this file to determine the
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maximum number of Virtual Functions (VFs) a PCIe physical
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function (PF) can support. Typically, this is the value reported
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in the PF's SR-IOV extended capability structure's TotalVFs
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element. Drivers have the ability at probe time to reduce the
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value read from this file via the pci_sriov_set_totalvfs()
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function.
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What: /sys/bus/pci/devices/.../sriov_numvfs
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Date: November 2012
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Contact: Donald Dutile <ddutile@redhat.com>
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Description:
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This file appears when a physical PCIe device supports SR-IOV.
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Userspace applications can read and write to this file to
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determine and control the enablement or disablement of Virtual
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Functions (VFs) on the physical function (PF). A read of this
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file will return the number of VFs that are enabled on this PF.
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A number written to this file will enable the specified
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number of VFs. A userspace application would typically read the
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file and check that the value is zero, and then write the number
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of VFs that should be enabled on the PF; the value written
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should be less than or equal to the value in the sriov_totalvfs
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file. A userspace application wanting to disable the VFs would
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write a zero to this file. The core ensures that valid values
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are written to this file, and returns errors when values are not
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valid. For example, writing a 2 to this file when sriov_numvfs
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is not 0 and not 2 already will return an error. Writing a 10
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when the value of sriov_totalvfs is 8 will return an error.
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@ -2,6 +2,9 @@
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Copyright (C) 2009 Intel Corporation
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Copyright (C) 2009 Intel Corporation
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Yu Zhao <yu.zhao@intel.com>
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Yu Zhao <yu.zhao@intel.com>
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Update: November 2012
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-- sysfs-based SRIOV enable-/disable-ment
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Donald Dutile <ddutile@redhat.com>
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1. Overview
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1. Overview
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@ -24,10 +27,21 @@ real existing PCI device.
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2.1 How can I enable SR-IOV capability
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2.1 How can I enable SR-IOV capability
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The device driver (PF driver) will control the enabling and disabling
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Multiple methods are available for SR-IOV enablement.
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of the capability via API provided by SR-IOV core. If the hardware
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In the first method, the device driver (PF driver) will control the
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has SR-IOV capability, loading its PF driver would enable it and all
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enabling and disabling of the capability via API provided by SR-IOV core.
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VFs associated with the PF.
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If the hardware has SR-IOV capability, loading its PF driver would
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enable it and all VFs associated with the PF. Some PF drivers require
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a module parameter to be set to determine the number of VFs to enable.
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In the second method, a write to the sysfs file sriov_numvfs will
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enable and disable the VFs associated with a PCIe PF. This method
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enables per-PF, VF enable/disable values versus the first method,
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which applies to all PFs of the same device. Additionally, the
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PCI SRIOV core support ensures that enable/disable operations are
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valid to reduce duplication in multiple drivers for the same
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checks, e.g., check numvfs == 0 if enabling VFs, ensure
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numvfs <= totalvfs.
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The second method is the recommended method for new/future VF devices.
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2.2 How can I use the Virtual Functions
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2.2 How can I use the Virtual Functions
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@ -40,13 +54,22 @@ requires device driver that is same as a normal PCI device's.
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3.1 SR-IOV API
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3.1 SR-IOV API
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To enable SR-IOV capability:
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To enable SR-IOV capability:
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(a) For the first method, in the driver:
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int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
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int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
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'nr_virtfn' is number of VFs to be enabled.
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'nr_virtfn' is number of VFs to be enabled.
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(b) For the second method, from sysfs:
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echo 'nr_virtfn' > \
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/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
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To disable SR-IOV capability:
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To disable SR-IOV capability:
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(a) For the first method, in the driver:
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void pci_disable_sriov(struct pci_dev *dev);
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void pci_disable_sriov(struct pci_dev *dev);
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(b) For the second method, from sysfs:
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echo 0 > \
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/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
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To notify SR-IOV core of Virtual Function Migration:
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To notify SR-IOV core of Virtual Function Migration:
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(a) In the driver:
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irqreturn_t pci_sriov_migration(struct pci_dev *dev);
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irqreturn_t pci_sriov_migration(struct pci_dev *dev);
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3.2 Usage example
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3.2 Usage example
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@ -88,6 +111,22 @@ static void dev_shutdown(struct pci_dev *dev)
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...
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...
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}
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}
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static int dev_sriov_configure(struct pci_dev *dev, int numvfs)
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{
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if (numvfs > 0) {
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...
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pci_enable_sriov(dev, numvfs);
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...
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return numvfs;
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}
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if (numvfs == 0) {
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....
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pci_disable_sriov(dev);
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...
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return 0;
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}
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}
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static struct pci_driver dev_driver = {
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static struct pci_driver dev_driver = {
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.name = "SR-IOV Physical Function driver",
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.name = "SR-IOV Physical Function driver",
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.id_table = dev_id_table,
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.id_table = dev_id_table,
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@ -96,4 +135,5 @@ static struct pci_driver dev_driver = {
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.suspend = dev_suspend,
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.suspend = dev_suspend,
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.resume = dev_resume,
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.resume = dev_resume,
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.shutdown = dev_shutdown,
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.shutdown = dev_shutdown,
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.sriov_configure = dev_sriov_configure,
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};
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};
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