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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Long Li <longli@microsoft.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 062/219] PCI: hv: Properly handle PCI bus
 remove
Thread-Topic: [PATCH AUTOSEL for 4.9 062/219] PCI: hv: Properly handle PCI bus
 remove
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Date:   Sat, 3 Mar 2018 22:28:32 +0000
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From: Long Li <longli@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 <xiaofwan@redhat.com>
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Sasha Levin <alexander.levin@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 =3D 0,
 	hv_pcibus_probed,
 	hv_pcibus_installed,
+	hv_pcibus_removed,
 	hv_pcibus_maximum
 };
=20
@@ -1489,13 +1490,24 @@ static void pci_devices_present_work(struct work_st=
ruct *work)
 		put_pcichild(hpdev, hv_pcidev_ref_initial);
 	}
=20
-	/* Tell the core to rescan bus because there may have been changes. */
-	if (hbus->state =3D=3D 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;
 	}
=20
 	up(&hbus->enum_sem);
@@ -2170,6 +2182,7 @@ static int hv_pci_probe(struct hv_device *hdev,
 	hbus =3D kzalloc(sizeof(*hbus), GFP_KERNEL);
 	if (!hbus)
 		return -ENOMEM;
+	hbus->state =3D hv_pcibus_init;
=20
 	/*
 	 * 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 =3D hv_pcibus_removed;
 	}
=20
 	ret =3D hv_send_resources_released(hdev);
--=20
2.14.1