PCI: Add sysfs sriov_drivers_autoprobe to control VF driver binding

Sometimes it is not desirable to bind SR-IOV VFs to drivers.  This can save
host side resource usage by VF instances that will be assigned to VMs.

Add a new PCI sysfs interface "sriov_drivers_autoprobe" to control that
from the PF.  To modify it, echo 0/n/N (disable probe) or 1/y/Y (enable
probe) to:

  /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe

Note that this must be done before enabling VFs.  The change will not take
effect if VFs are already enabled.  Simply, one can disable VFs by setting
sriov_numvfs to 0, choose whether to probe or not, and then re-enable the
VFs by restoring sriov_numvfs.

[bhelgaas: changelog, ABI doc]
Signed-off-by: Bodong Wang <bodong@mellanox.com>
Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Bodong Wang 2017-04-13 01:51:40 +03:00 committed by Bjorn Helgaas
parent f65fd1aa4f
commit 0e7df22401
6 changed files with 82 additions and 4 deletions

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@ -301,3 +301,25 @@ Contact: Emil Velikov <emil.l.velikov@gmail.com>
Description:
This file contains the revision field of the the PCI device.
The value comes from device config space. The file is read only.
What: /sys/bus/pci/devices/.../sriov_drivers_autoprobe
Date: April 2017
Contact: Bodong Wang<bodong@mellanox.com>
Description:
This file is associated with the PF of a device that
supports SR-IOV. It determines whether newly-enabled VFs
are immediately bound to a driver. It initially contains
1, which means the kernel automatically binds VFs to a
compatible driver immediately after they are enabled. If
an application writes 0 to the file before enabling VFs,
the kernel will not bind VFs to a driver.
A typical use case is to write 0 to this file, then enable
VFs, then assign the newly-created VFs to virtual machines.
Note that changing this file does not affect already-
enabled VFs. In this scenario, the user must first disable
the VFs, write 0 to sriov_drivers_autoprobe, then re-enable
the VFs.
This is similar to /sys/bus/pci/drivers_autoprobe, but
affects only the VFs associated with a specific PF.

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@ -68,6 +68,18 @@ To disable SR-IOV capability:
echo 0 > \
/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
To enable auto probing VFs by a compatible driver on the host, run
command below before enabling SR-IOV capabilities. This is the
default behavior.
echo 1 > \
/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
To disable auto probing VFs by a compatible driver on the host, run
command below before enabling SR-IOV capabilities. Updating this
entry will not affect VFs which are already probed.
echo 0 > \
/sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
3.2 Usage example
Following piece of code illustrates the usage of the SR-IOV API.

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@ -450,6 +450,7 @@ found:
iov->total_VFs = total;
iov->pgsz = pgsz;
iov->self = dev;
iov->drivers_autoprobe = true;
pci_read_config_dword(dev, pos + PCI_SRIOV_CAP, &iov->cap);
pci_read_config_byte(dev, pos + PCI_SRIOV_FUNC_LINK, &iov->link);
if (pci_pcie_type(dev) == PCI_EXP_TYPE_RC_END)

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@ -394,6 +394,18 @@ void __weak pcibios_free_irq(struct pci_dev *dev)
{
}
#ifdef CONFIG_PCI_IOV
static inline bool pci_device_can_probe(struct pci_dev *pdev)
{
return (!pdev->is_virtfn || pdev->physfn->sriov->drivers_autoprobe);
}
#else
static inline bool pci_device_can_probe(struct pci_dev *pdev)
{
return true;
}
#endif
static int pci_device_probe(struct device *dev)
{
int error;
@ -405,10 +417,12 @@ static int pci_device_probe(struct device *dev)
return error;
pci_dev_get(pci_dev);
error = __pci_device_probe(drv, pci_dev);
if (error) {
pcibios_free_irq(pci_dev);
pci_dev_put(pci_dev);
if (pci_device_can_probe(pci_dev)) {
error = __pci_device_probe(drv, pci_dev);
if (error) {
pcibios_free_irq(pci_dev);
pci_dev_put(pci_dev);
}
}
return error;

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@ -526,10 +526,37 @@ exit:
return count;
}
static ssize_t sriov_drivers_autoprobe_show(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct pci_dev *pdev = to_pci_dev(dev);
return sprintf(buf, "%u\n", pdev->sriov->drivers_autoprobe);
}
static ssize_t sriov_drivers_autoprobe_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct pci_dev *pdev = to_pci_dev(dev);
bool drivers_autoprobe;
if (kstrtobool(buf, &drivers_autoprobe) < 0)
return -EINVAL;
pdev->sriov->drivers_autoprobe = drivers_autoprobe;
return count;
}
static struct device_attribute sriov_totalvfs_attr = __ATTR_RO(sriov_totalvfs);
static struct device_attribute sriov_numvfs_attr =
__ATTR(sriov_numvfs, (S_IRUGO|S_IWUSR|S_IWGRP),
sriov_numvfs_show, sriov_numvfs_store);
static struct device_attribute sriov_drivers_autoprobe_attr =
__ATTR(sriov_drivers_autoprobe, (S_IRUGO|S_IWUSR|S_IWGRP),
sriov_drivers_autoprobe_show, sriov_drivers_autoprobe_store);
#endif /* CONFIG_PCI_IOV */
static ssize_t driver_override_store(struct device *dev,
@ -1549,6 +1576,7 @@ static struct attribute_group pci_dev_hp_attr_group = {
static struct attribute *sriov_dev_attrs[] = {
&sriov_totalvfs_attr.attr,
&sriov_numvfs_attr.attr,
&sriov_drivers_autoprobe_attr.attr,
NULL,
};

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@ -272,6 +272,7 @@ struct pci_sriov {
struct pci_dev *self; /* this PF */
struct mutex lock; /* lock for setting sriov_numvfs in sysfs */
resource_size_t barsz[PCI_SRIOV_NUM_BARS]; /* VF BAR size */
bool drivers_autoprobe; /* auto probing of VFs by driver */
};
#ifdef CONFIG_PCI_ATS