140 строки
3.9 KiB
Plaintext
140 строки
3.9 KiB
Plaintext
PCI Express I/O Virtualization Howto
|
|
Copyright (C) 2009 Intel Corporation
|
|
Yu Zhao <yu.zhao@intel.com>
|
|
|
|
Update: November 2012
|
|
-- sysfs-based SRIOV enable-/disable-ment
|
|
Donald Dutile <ddutile@redhat.com>
|
|
|
|
1. Overview
|
|
|
|
1.1 What is SR-IOV
|
|
|
|
Single Root I/O Virtualization (SR-IOV) is a PCI Express Extended
|
|
capability which makes one physical device appear as multiple virtual
|
|
devices. The physical device is referred to as Physical Function (PF)
|
|
while the virtual devices are referred to as Virtual Functions (VF).
|
|
Allocation of the VF can be dynamically controlled by the PF via
|
|
registers encapsulated in the capability. By default, this feature is
|
|
not enabled and the PF behaves as traditional PCIe device. Once it's
|
|
turned on, each VF's PCI configuration space can be accessed by its own
|
|
Bus, Device and Function Number (Routing ID). And each VF also has PCI
|
|
Memory Space, which is used to map its register set. VF device driver
|
|
operates on the register set so it can be functional and appear as a
|
|
real existing PCI device.
|
|
|
|
2. User Guide
|
|
|
|
2.1 How can I enable SR-IOV capability
|
|
|
|
Multiple methods are available for SR-IOV enablement.
|
|
In the first method, the device driver (PF driver) will control the
|
|
enabling and disabling of the capability via API provided by SR-IOV core.
|
|
If the hardware has SR-IOV capability, loading its PF driver would
|
|
enable it and all VFs associated with the PF. Some PF drivers require
|
|
a module parameter to be set to determine the number of VFs to enable.
|
|
In the second method, a write to the sysfs file sriov_numvfs will
|
|
enable and disable the VFs associated with a PCIe PF. This method
|
|
enables per-PF, VF enable/disable values versus the first method,
|
|
which applies to all PFs of the same device. Additionally, the
|
|
PCI SRIOV core support ensures that enable/disable operations are
|
|
valid to reduce duplication in multiple drivers for the same
|
|
checks, e.g., check numvfs == 0 if enabling VFs, ensure
|
|
numvfs <= totalvfs.
|
|
The second method is the recommended method for new/future VF devices.
|
|
|
|
2.2 How can I use the Virtual Functions
|
|
|
|
The VF is treated as hot-plugged PCI devices in the kernel, so they
|
|
should be able to work in the same way as real PCI devices. The VF
|
|
requires device driver that is same as a normal PCI device's.
|
|
|
|
3. Developer Guide
|
|
|
|
3.1 SR-IOV API
|
|
|
|
To enable SR-IOV capability:
|
|
(a) For the first method, in the driver:
|
|
int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
|
|
'nr_virtfn' is number of VFs to be enabled.
|
|
(b) For the second method, from sysfs:
|
|
echo 'nr_virtfn' > \
|
|
/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
|
|
|
|
To disable SR-IOV capability:
|
|
(a) For the first method, in the driver:
|
|
void pci_disable_sriov(struct pci_dev *dev);
|
|
(b) For the second method, from sysfs:
|
|
echo 0 > \
|
|
/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
|
|
|
|
To notify SR-IOV core of Virtual Function Migration:
|
|
(a) In the driver:
|
|
irqreturn_t pci_sriov_migration(struct pci_dev *dev);
|
|
|
|
3.2 Usage example
|
|
|
|
Following piece of code illustrates the usage of the SR-IOV API.
|
|
|
|
static int dev_probe(struct pci_dev *dev, const struct pci_device_id *id)
|
|
{
|
|
pci_enable_sriov(dev, NR_VIRTFN);
|
|
|
|
...
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void dev_remove(struct pci_dev *dev)
|
|
{
|
|
pci_disable_sriov(dev);
|
|
|
|
...
|
|
}
|
|
|
|
static int dev_suspend(struct pci_dev *dev, pm_message_t state)
|
|
{
|
|
...
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int dev_resume(struct pci_dev *dev)
|
|
{
|
|
...
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void dev_shutdown(struct pci_dev *dev)
|
|
{
|
|
...
|
|
}
|
|
|
|
static int dev_sriov_configure(struct pci_dev *dev, int numvfs)
|
|
{
|
|
if (numvfs > 0) {
|
|
...
|
|
pci_enable_sriov(dev, numvfs);
|
|
...
|
|
return numvfs;
|
|
}
|
|
if (numvfs == 0) {
|
|
....
|
|
pci_disable_sriov(dev);
|
|
...
|
|
return 0;
|
|
}
|
|
}
|
|
|
|
static struct pci_driver dev_driver = {
|
|
.name = "SR-IOV Physical Function driver",
|
|
.id_table = dev_id_table,
|
|
.probe = dev_probe,
|
|
.remove = dev_remove,
|
|
.suspend = dev_suspend,
|
|
.resume = dev_resume,
|
|
.shutdown = dev_shutdown,
|
|
.sriov_configure = dev_sriov_configure,
|
|
};
|