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, 18 insertions, 4 deletions

diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
index afa72717a979..f99f7fe749b8 100644
--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -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;