[PATCH RESEND 1/2] PCI: Extend isolated function probing to s390

Niklas Schnelle
2022-04-04T09:54:31Z

Like the jailhouse hypervisor s390's PCI architecture allows passing
isolated PCI functions to an OS instance. As of now this is was not
utilized even with multi-function support as the s390 PCI code makes
sure that only virtual PCI busses including a function with devfn 0 are
presented to the PCI subsystem. A subsequent change will remove this
restriction.

Allow probing such functions by replacing the existing check for
jailhouse_paravirt() with a new hypervisor_isolated_pci_functions()
helper.

Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
---
drivers/pci/probe.c | 4 ++--
include/linux/hypervisor.h | 9 +++++++++
2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 17a969942d37..e8fd89a1f984 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2869,11 +2869,11 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
nr_devs = pci_scan_slot(bus, devfn);

/*
- * The Jailhouse hypervisor may pass individual functions of a
+ * Some hypervisors 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) {
+ if (hypervisor_isolated_pci_functions() && nr_devs == 0) {
for (fn = 1; fn < 8; fn++) {
dev = pci_scan_single_device(bus, devfn + fn);
if (dev)
diff --git a/include/linux/hypervisor.h b/include/linux/hypervisor.h
index fc08b433c856..52abd459f9a3 100644
--- a/include/linux/hypervisor.h
+++ b/include/linux/hypervisor.h
@@ -32,4 +32,13 @@ static inline bool jailhouse_paravirt(void)

#endif /* !CONFIG_X86 */

+static inline bool hypervisor_isolated_pci_functions(void)
+{
+ if (IS_ENABLED(CONFIG_S390))
+ return true;
+ else
+ return jailhouse_paravirt();
+}
+
+
#endif /* __LINUX_HYPEVISOR_H */
--
2.32.0