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PCI: SRIOV control and status via sysfs (documentation)

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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>
This commit is contained in:
Donald Dutile 2012-11-27 22:31:37 -05:00 committed by Bjorn Helgaas
parent 1452cd76a9
commit 2597ba763f
2 changed files with 78 additions and 4 deletions
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34
Documentation/ABI/testing/sysfs-bus-pci
View File

@ -222,3 +222,37 @@ Description:
satisfied too. Reading this attribute will show the current
value of d3cold_allowed bit. Writing this attribute will set
the value of d3cold_allowed bit.
What: /sys/bus/pci/devices/.../sriov_totalvfs
Date: November 2012
Contact: Donald Dutile <ddutile@redhat.com>
Description:
This file appears when a physical PCIe device supports SR-IOV.
Userspace applications can read this file to determine the
maximum number of Virtual Functions (VFs) a PCIe physical
function (PF) can support. Typically, this is the value reported
in the PF's SR-IOV extended capability structure's TotalVFs
element. Drivers have the ability at probe time to reduce the
value read from this file via the pci_sriov_set_totalvfs()
function.
What: /sys/bus/pci/devices/.../sriov_numvfs
Date: November 2012
Contact: Donald Dutile <ddutile@redhat.com>
Description:
This file appears when a physical PCIe device supports SR-IOV.
Userspace applications can read and write to this file to
determine and control the enablement or disablement of Virtual
Functions (VFs) on the physical function (PF). A read of this
file will return the number of VFs that are enabled on this PF.
A number written to this file will enable the specified
number of VFs. A userspace application would typically read the
file and check that the value is zero, and then write the number
of VFs that should be enabled on the PF; the value written
should be less than or equal to the value in the sriov_totalvfs
file. A userspace application wanting to disable the VFs would
write a zero to this file. The core ensures that valid values
are written to this file, and returns errors when values are not
valid. For example, writing a 2 to this file when sriov_numvfs
is not 0 and not 2 already will return an error. Writing a 10
when the value of sriov_totalvfs is 8 will return an error.

48
Documentation/PCI/pci-iov-howto.txt
View File

@ -2,6 +2,9 @@
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
@ -24,10 +27,21 @@ real existing PCI device.
2.1 How can I enable SR-IOV capability
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.
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
@ -40,13 +54,22 @@ requires device driver that is same as a normal PCI device's.
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
@ -88,6 +111,22 @@ 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,
@ -96,4 +135,5 @@ static struct pci_driver dev_driver = {
.suspend = dev_suspend,
.resume = dev_resume,
.shutdown = dev_shutdown,
.sriov_configure = dev_sriov_configure,
};