[SRU][Xenial][PATCH 2/3] UBUNTU: SAUCE: pci-hyperv: properly handle pci bus remove

[Joseph Salisbury]

From: Long Li <longli at microsoft.com>

BugLink: http://bugs.launchpad.net/bugs/1665097

hv_pci_devices_present is called in hv_pci_remove when we remove a PCI 
device from host (e.g. by disabling SRIOV on a device). In hv_pci_remove, 
the bus is already removed before the call, so we don't need to rescan the 
bus in the workqueue scheduled from hv_pci_devices_present. By introducing 
status hv_pcibus_removed, we can avoid this situation.

Signed-off-by: Long Li <longli at microsoft.com>
Reported-by: Xiaofeng Wang <xiaofwan at redhat.com>
Signed-off-by: Joseph Salisbury <joseph.salisbury at canonical.com>
---
 drivers/pci/host/pci-hyperv.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index b0ee99c6..d4a7994 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -349,6 +349,7 @@ enum hv_pcibus_state {
 	hv_pcibus_init = 0,
 	hv_pcibus_probed,
 	hv_pcibus_installed,
+	hv_pcibus_removed,
 	hv_pcibus_maximum
 };
 
@@ -1484,13 +1485,24 @@ static void pci_devices_present_work(struct work_struct *work)
 		put_pcichild(hpdev, hv_pcidev_ref_initial);
 	}
 
-	/* Tell the core to rescan bus because there may have been changes. */
-	if (hbus->state == hv_pcibus_installed) {
+	switch (hbus->state) {
+	case hv_pcibus_installed:
+		/*
+		 * Tell the core to rescan bus
+		 * because there may have been changes.
+		 */
 		pci_lock_rescan_remove();
 		pci_scan_child_bus(hbus->pci_bus);
 		pci_unlock_rescan_remove();
-	} else {
+		break;
+
+	case hv_pcibus_init:
+	case hv_pcibus_probed:
 		survey_child_resources(hbus);
+		break;
+
+	default:
+		break;
 	}
 
 	up(&hbus->enum_sem);
@@ -2166,6 +2178,7 @@ static int hv_pci_probe(struct hv_device *hdev,
 	hbus = kzalloc(sizeof(*hbus), GFP_KERNEL);
 	if (!hbus)
 		return -ENOMEM;
+	hbus->state = hv_pcibus_init;
 
 	/*
 	 * The PCI bus "domain" is what is called "segment" in ACPI and
@@ -2308,6 +2321,7 @@ static int hv_pci_remove(struct hv_device *hdev)
 		pci_stop_root_bus(hbus->pci_bus);
 		pci_remove_root_bus(hbus->pci_bus);
 		pci_unlock_rescan_remove();
+		hbus->state = hv_pcibus_removed;
 	}
 
 	ret = hv_send_resources_released(hdev);
-- 
2.7.4