PCI: Provide method to reduce the number of total VFs supported

Some implementations of SRIOV provide a capability structure
value of TotalVFs that is greater than what the software can support.
Provide a method to reduce the capability structure reported value
to the value the driver can support.
This ensures sysfs reports the current capability of the system,
hardware and software.
Example for its use: igb & ixgbe -- report 8 & 64 as TotalVFs,
but drivers only support 7 & 63 maximum.

Signed-off-by: Donald Dutile <ddutile@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index aeccc911abb8..f6781e42d00d 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -735,3 +735,50 @@ int pci_num_vf(struct pci_dev *dev)
 		return dev->sriov->nr_virtfn;
 }
 EXPORT_SYMBOL_GPL(pci_num_vf);
+
+/**
+ * pci_sriov_set_totalvfs -- reduce the TotalVFs available
+ * @dev: the PCI PF device
+ * numvfs: number that should be used for TotalVFs supported
+ *
+ * Should be called from PF driver's probe routine with
+ * device's mutex held.
+ *
+ * Returns 0 if PF is an SRIOV-capable device and
+ * value of numvfs valid. If not a PF with VFS, return -EINVAL;
+ * if VFs already enabled, return -EBUSY.
+ */
+int pci_sriov_set_totalvfs(struct pci_dev *dev, u16 numvfs)
+{
+	if (!dev || !dev->is_physfn || (numvfs > dev->sriov->total))
+		return -EINVAL;
+
+	/* Shouldn't change if VFs already enabled */
+	if (dev->sriov->ctrl & PCI_SRIOV_CTRL_VFE)
+		return -EBUSY;
+	else
+		dev->sriov->drvttl = numvfs;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(pci_sriov_set_totalvfs);
+
+/**
+ * pci_sriov_get_totalvfs -- get total VFs supported on this devic3
+ * @dev: the PCI PF device
+ *
+ * For a PCIe device with SRIOV support, return the PCIe
+ * SRIOV capability value of TotalVFs or the value of drvttl
+ * if the driver reduced it.  Otherwise, -EINVAL.
+ */
+int pci_sriov_get_totalvfs(struct pci_dev *dev)
+{
+	if (!dev || !dev->is_physfn)
+		return -EINVAL;
+
+	if (dev->sriov->drvttl)
+		return dev->sriov->drvttl;
+	else
+		return dev->sriov->total;
+}
+EXPORT_SYMBOL_GPL(pci_sriov_get_totalvfs);