Re: [PATCH v6 4/5] PCI: Extend isolated function probing to s390

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On 6/28/22 16:30, Niklas Schnelle wrote:
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@xxxxxxxxxxx>
Signed-off-by: Niklas Schnelle <schnelle@xxxxxxxxxxxxx>
---
  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 a18e07e6a7df..156dd13594b8 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2667,7 +2667,7 @@ 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();

I would spare the else,

Another remark, shouldn't it be the last patch?

otherwise LGTM

Reviewed-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>


+}
+
  #endif /* __LINUX_HYPEVISOR_H */


--
Pierre Morel
IBM Lab Boeblingen



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