Commit 0e7df224 authored by Bodong Wang's avatar Bodong Wang Committed by Bjorn Helgaas
Browse files

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: default avatarBodong Wang <bodong@mellanox.com>
Signed-off-by: default avatarEli Cohen <eli@mellanox.com>
Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: default avatarGavin Shan <gwshan@linux.vnet.ibm.com>
Reviewed-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent f65fd1aa

Documentation/ABI/testing/sysfs-bus-pci

+22 −0
Original line number Diff line number Diff line
@@ -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.

Documentation/PCI/pci-iov-howto.txt

+12 −0
Original line number Diff line number Diff line
@@ -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.

drivers/pci/iov.c

+1 −0
Original line number Diff line number Diff line
@@ -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)

drivers/pci/pci-driver.c

+18 −4
Original line number Diff line number Diff line
@@ -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;
@@ -405,11 +417,13 @@ static int pci_device_probe(struct device *dev) 
		return error;



	pci_dev_get(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;

}

drivers/pci/pci-sysfs.c

+28 −0
Original line number Diff line number Diff line
@@ -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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