[PATCH v6 3/5] PCI: Move jailhouse's isolated function handling to pci_scan_slot()

Niklas Schnelle
2022-06-28T14:31:16Z

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 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.

Cc: Jan Kiszka <jan.kiszka@siemens.com>
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 | 30 ++++++++++--------------------
1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2c737dce757e..a18e07e6a7df 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2662,8 +2662,13 @@ 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 which passes through individual PCI
+ * functions.
+ */
+ if (!jailhouse_paravirt())
+ break;
}
fn = next_fn(bus, dev, fn);
} while (fn >= 0);
@@ -2862,29 +2867,14 @@ 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);
--
2.32.0