[PATCH AUTOSEL for 4.9 062/219] PCI: hv: Properly handle PCI bus remove

[Sasha Levin]

From: Long Li <lon...@microsoft.com>

[ Upstream commit d3a78d8bf759d8848339dcc367c4c1678b57a08b ]

hv_pci_devices_present() is called in hv_pci_remove() when we remove a PCI
device from the host, e.g., by disabling SR-IOV 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 bus state hv_pcibus_removed, we can avoid this situation.

Reported-by: Xiaofeng Wang <xiaof...@redhat.com>
Signed-off-by: Long Li <lon...@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelg...@google.com>
Acked-by: K. Y. Srinivasan <k...@microsoft.com>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.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 dafb4cdb2b7f..43aa630f419a 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -351,6 +351,7 @@ enum hv_pcibus_state {
        hv_pcibus_init = 0,
        hv_pcibus_probed,
        hv_pcibus_installed,
+       hv_pcibus_removed,
        hv_pcibus_maximum
 };
 
@@ -1489,13 +1490,24 @@ 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);
@@ -2170,6 +2182,7 @@ 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
@@ -2312,6 +2325,7 @@ 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);
-- 
2.14.1