linux-kernel - [PATCH v4 3/4] PCI: Extend isolated function probing to s390

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Date:   Fri, 22 Apr 2022 15:28:57 +0200
From:   Niklas Schnelle <schnelle@...ux.ibm.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Pierre Morel <pmorel@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-s390@...r.kernel.org, linux-pci@...r.kernel.org
Subject: [PATCH v4 3/4] PCI: Extend isolated function probing to s390

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.

Cc: Jan Kiszka <jan.kiszka@...mens.com>
Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
---
 drivers/pci/probe.c        | 2 +-
 include/linux/hypervisor.h | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ce4e41a7d358..cbf91bd389d6 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2664,7 +2664,7 @@ int pci_scan_slot(struct pci_bus *bus, int devfn)
 			 * a hypervisor which passes through individual PCI
 			 * functions.
 			 */
-			if (!jailhouse_paravirt())
+			if (!hypervisor_isolated_pci_functions())
 				break;
 		}
 		fn = next_fn(bus, dev, fn);
diff --git a/include/linux/hypervisor.h b/include/linux/hypervisor.h
index fc08b433c856..33b1c0482aac 100644
--- a/include/linux/hypervisor.h
+++ b/include/linux/hypervisor.h
@@ -32,4 +32,12 @@ 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