PCI: Cache the VF device ID in the SR-IOV structure

Cache the VF device ID in the SR-IOV structure and use it instead of
reading it over and over from the PF config space capability.
Signed-off-by: Filippo Sironi <sironi@amazon.de>
[bhelgaas: rename to "vf_device" to match pci_dev->device]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/iov.c

@@ -134,7 +134,7 @@ int pci_iov_add_virtfn(struct pci_dev *dev, int id)
 
 	virtfn->devfn = pci_iov_virtfn_devfn(dev, id);
 	virtfn->vendor = dev->vendor;
-	pci_read_config_word(dev, iov->pos + PCI_SRIOV_VF_DID, &virtfn->device);
+	virtfn->device = iov->vf_device;
 	rc = pci_setup_device(virtfn);
 	if (rc)
 		goto failed0;
@@ -441,6 +441,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
 	iov->nres = nres;
 	iov->ctrl = ctrl;
 	iov->total_VFs = total;
+	pci_read_config_word(dev, pos + PCI_SRIOV_VF_DID, &iov->vf_device);
 	iov->pgsz = pgsz;
 	iov->self = dev;
 	iov->drivers_autoprobe = true;
@@ -716,7 +717,7 @@ int pci_vfs_assigned(struct pci_dev *dev)
 	 * determine the device ID for the VFs, the vendor ID will be the
 	 * same as the PF so there is no need to check for that one
 	 */
-	pci_read_config_word(dev, dev->sriov->pos + PCI_SRIOV_VF_DID, &dev_id);
+	dev_id = dev->sriov->vf_device;
 
 	/* loop through all the VFs to see if we own any that are assigned */
 	vfdev = pci_get_device(dev->vendor, dev_id, NULL);

drivers/pci/pci.h

@@ -263,6 +263,7 @@ struct pci_sriov {
 	u16 num_VFs;		/* number of VFs available */
 	u16 offset;		/* first VF Routing ID offset */
 	u16 stride;		/* following VF stride */
+	u16 vf_device;		/* VF device ID */
 	u32 pgsz;		/* page size for BAR alignment */
 	u8 link;		/* Function Dependency Link */
 	u8 max_VF_buses;	/* max buses consumed by VFs */