[PATCH v2 2/4] PCI: Move jailhouse's isolated function handling to pci_scan_slot()

Niklas Schnelle
2022-04-12T14:30:54Z

The special case of the jailhouse hypervisor passing through individual
PCI functions handles scanning for PCI functions even if function 0 does
not exist. Currently this is done with an extra loop duplicating the one
in pci_scan_slot(). By incorporating the check for jailhouse_paravirt()
into next_fn() we can instead do this as part of the normal
pci_scan_slot(). 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>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
drivers/pci/probe.c | 25 ++++++-------------------
1 file changed, 6 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 389aa1f9cb2c..8100e044dfc5 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2602,10 +2602,11 @@ static int next_fn(struct pci_bus *bus, struct pci_dev *dev, int fn)
if (dev && !dev->multifunction)
return -ENODEV;
/*
- * A function 0 is required but multifunction devices may
- * be non-contiguous so dev can be NULL otherwise.
+ * Usually a function 0 is required but the jailhouse hypervisor may
+ * pass individual functions. For non-contiguous multifunction devices
+ * some functions may also be missing.
*/
- if (!fn && !dev)
+ if (!fn && !dev && !jailhouse_paravirt())
return -ENODEV;
return (fn <= 6) ? fn + 1 : -ENODEV;
}
@@ -2855,30 +2856,16 @@ 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) {
+ 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;
- }
- }
- }
-
/* Reserve buses for SR-IOV capability */
used_buses = pci_iov_bus_range(bus);
max += used_buses;
--
2.32.0