s390/pci: Fix handling of isolated VFs

BugLink: https://bugs.launchpad.net/bugs/2102118

commit 2844ddbd540fc84d7571cca65d6c43088e4d6952 upstream.

In contrast to the commit message of the fixed commit VFs whose parent
PF is not configured are not always isolated, that is put on their own
PCI domain. This is because for VFs to be added to an existing PCI
domain it is enough for that PCI domain to share the same topology ID or
PCHID. Such a matching PCI domain without a parent PF may exist when
a PF from the same PCI card created the domain with the VF being a child
of a different, non accessible, PF. While not causing technical issues
it makes the rules which VFs are isolated inconsistent.

Fix this by explicitly checking that the parent PF exists on the PCI
domain determined by the topology ID or PCHID before registering the VF.
This works because a parent PF which is under control of this Linux
instance must be enabled and configured at the point where its child VFs
appear because otherwise SR-IOV could not have been enabled on the
parent.

Fixes: 25f39d3dcb48 ("s390/pci: Ignore RID for isolated VFs")
Cc: stable@vger.kernel.org
Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 01df870db957eae7d031722f2ca90642ac526cd6 linux-6.12.y)
[koichiroden: follow-up fix from v6.12.16]
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

arch/s390/pci/pci_bus.c

@@ -331,6 +331,17 @@ error:
 	return rc;
 }
 
+static bool zpci_bus_is_isolated_vf(struct zpci_bus *zbus, struct zpci_dev *zdev)
+{
+	struct pci_dev *pdev;
+
+	pdev = zpci_iov_find_parent_pf(zbus, zdev);
+	if (!pdev)
+		return true;
+	pci_dev_put(pdev);
+	return false;
+}
+
 int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
 {
 	bool topo_is_tid = zdev->tid_avail;
@@ -345,6 +356,15 @@ int zpci_bus_device_register(struct zpci_dev *zdev, struct pci_ops *ops)
 
 	topo = topo_is_tid ? zdev->tid : zdev->pchid;
 	zbus = zpci_bus_get(topo, topo_is_tid);
+	/*
+	 * An isolated VF gets its own domain/bus even if there exists
+	 * a matching domain/bus already
+	 */
+	if (zbus && zpci_bus_is_isolated_vf(zbus, zdev)) {
+		zpci_bus_put(zbus);
+		zbus = NULL;
+	}
+
 	if (!zbus) {
 		zbus = zpci_bus_alloc(topo, topo_is_tid);
 		if (!zbus)

arch/s390/pci/pci_iov.c

@@ -74,7 +74,7 @@ static int zpci_iov_link_virtfn(struct pci_dev *pdev, struct pci_dev *virtfn, in
  * found. If the function is not a VF or has no RequesterID information,
  * NULL is returned as well.
  */
-static struct pci_dev *zpci_iov_find_parent_pf(struct zpci_bus *zbus, struct zpci_dev *zdev)
+struct pci_dev *zpci_iov_find_parent_pf(struct zpci_bus *zbus, struct zpci_dev *zdev)
 {
 	int i, vfid, devfn, cand_devfn;
 	struct pci_dev *pdev;

arch/s390/pci/pci_iov.h

@@ -17,6 +17,8 @@ void zpci_iov_map_resources(struct pci_dev *pdev);
 
 int zpci_iov_setup_virtfn(struct zpci_bus *zbus, struct pci_dev *virtfn, int vfn);
 
+struct pci_dev *zpci_iov_find_parent_pf(struct zpci_bus *zbus, struct zpci_dev *zdev);
+
 #else /* CONFIG_PCI_IOV */
 static inline void zpci_iov_remove_virtfn(struct pci_dev *pdev, int vfn) {}
 
@@ -26,5 +28,10 @@ static inline int zpci_iov_setup_virtfn(struct zpci_bus *zbus, struct pci_dev *v
 {
 	return 0;
 }
+
+static inline struct pci_dev *zpci_iov_find_parent_pf(struct zpci_bus *zbus, struct zpci_dev *zdev)
+{
+	return NULL;
+}
 #endif /* CONFIG_PCI_IOV */
 #endif /* __S390_PCI_IOV_h */