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>

1 files changed, 28 insertions, 0 deletions

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 25d010d..369c999 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -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,
 };