PCI: Move jailhouse's isolated function handling to pci_scan_slot()

The special case of the jailhouse hypervisor passing through individual PCI
functions handles scanning for PCI functions even if function 0 does not
exist. Previously this was done with an extra loop duplicating the one in
pci_scan_slot(). By incorporating the check for jailhouse_paravirt() into
pci_scan_slot() we can instead do this as part of the normal slot scan.
Note that with the assignment of dev->multifunction gated by fn > 0 we set
dev->multifunction unconditionally for all functions if function 0 is
missing just as in the existing jailhouse loop.

The only functional change is that we now call pcie_aspm_init_link_state()
for these functions, but this already happened if function 0 was passed
through and should not be a problem.

Link: https://lore.kernel.org/linux-pci/20220408224514.GA353445@bhelgaas/
Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20220628143100.3228092-4-schnelle@linux.ibm.com
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index d62885519df3ed8fabb7ecdb346ee74ffcbbb337..1f91ed67b5c57a56a92964c52a5a80015b0f0086 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2663,8 +2663,13 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
                        if (fn > 0)
                                dev->multifunction = 1;
                } else if (fn == 0) {
-                       /* function 0 is required */
-                       break;
+                       /*
+                        * Function 0 is required unless we are running on
+                        * a hypervisor that passes through individual PCI
+                        * functions.
+                        */
+                       if (!jailhouse_paravirt())
+                               break;
                }
                fn = next_fn(bus, dev, fn);
        } while (fn >= 0);
@@ -2863,29 +2868,14 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
 {
        unsigned int used_buses, normal_bridges = 0, hotplug_bridges = 0;
        unsigned int start = bus->busn_res.start;
-       unsigned int devfn, fn, cmax, max = start;
+       unsigned int devfn, cmax, max = start;
        struct pci_dev *dev;
-       int nr_devs;
 
        dev_dbg(&bus->dev, "scanning bus\n");
 
        /* Go find them, Rover! */
-       for (devfn = 0; devfn < 256; devfn += 8) {
-               nr_devs = pci_scan_slot(bus, devfn);
-
-               /*
-                * The Jailhouse hypervisor may pass individual functions of a
-                * multi-function device to a guest without passing function 0.
-                * Look for them as well.
-                */
-               if (jailhouse_paravirt() && nr_devs == 0) {
-                       for (fn = 1; fn < 8; fn++) {
-                               dev = pci_scan_single_device(bus, devfn + fn);
-                               if (dev)
-                                       dev->multifunction = 1;
-                       }
-               }
-       }
+       for (devfn = 0; devfn < 256; devfn += 8)
+               pci_scan_slot(bus, devfn);
 
        /* Reserve buses for SR-IOV capability */
        used_buses = pci_iov_bus_range(bus);