From 0f4bd8014db515999493baaa75d506cc8026c462 Mon Sep 17 00:00:00 2001
From: Mika Westerberg <mika.westerberg@linux.intel.com>
Date: Thu, 9 Nov 2017 14:15:08 +0300
Subject: [PATCH] PCI: hotplug: Drop checking of PCI_BRIDGE_CONTROL in
 *_unconfigure_device()
Git-commit: 0f4bd8014db515999493baaa75d506cc8026c462
Patch-mainline: v4.16
References: FATE#326302


When removing a bridge, pciehp_unconfigure_device() reads the
PCI_BRIDGE_CONTROL byte.  If this is a surprise hot-unplug, the device is
already gone and the read returns ~0, which pciehp_unconfigure_device()
interprets as having PCI_BRIDGE_CTL_VGA set.  This results in failure of
the remove operation:

  pciehp 0000:00:1c.0:pcie004: Slot(0): Link Down
  pciehp 0000:00:1c.0:pcie004: Slot(0): Card present
  pciehp 0000:00:1c.0:pcie004: Cannot remove display device 0000:01:00.0

Because of this the hierarchy is left untouched preventing further hotplug
operations.

Now, it is not clear why the check is there in the first place and why we
would like to prevent removing a bridge if it has PCI_BRIDGE_CTL_VGA set.
In case of PCIe surprise hot-unplug, it would not even be possible to
prevent the removal.

Given this and the issue described above, I think it makes sense to drop
the whole PCI_BRIDGE_CONTROL check from pciehp_unconfigure_device().  While
there do the same for shpchp_configure_device() based on the same reasoning
and the fact that the same bug might trigger in standard PCI hotplug as
well.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/pci/hotplug/pciehp_pci.c | 12 ------------
 drivers/pci/hotplug/shpchp_pci.c | 12 ------------
 2 files changed, 24 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c
index 2a1ca020cf5a..acc360d1a1fb 100644
--- a/drivers/pci/hotplug/pciehp_pci.c
+++ b/drivers/pci/hotplug/pciehp_pci.c
@@ -79,7 +79,6 @@ int pciehp_configure_device(struct slot *p_slot)
 int pciehp_unconfigure_device(struct slot *p_slot)
 {
 	int rc = 0;
-	u8 bctl = 0;
 	u8 presence = 0;
 	struct pci_dev *dev, *temp;
 	struct pci_bus *parent = p_slot->ctrl->pcie->port->subordinate;
@@ -101,17 +100,6 @@ int pciehp_unconfigure_device(struct slot *p_slot)
 	list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
 					 bus_list) {
 		pci_dev_get(dev);
-		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && presence) {
-			pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl);
-			if (bctl & PCI_BRIDGE_CTL_VGA) {
-				ctrl_err(ctrl,
-					 "Cannot remove display device %s\n",
-					 pci_name(dev));
-				pci_dev_put(dev);
-				rc = -EINVAL;
-				break;
-			}
-		}
 		if (!presence) {
 			pci_dev_set_disconnected(dev, NULL);
 			if (pci_has_subordinate(dev))
diff --git a/drivers/pci/hotplug/shpchp_pci.c b/drivers/pci/hotplug/shpchp_pci.c
index ea63db58b4b1..79f1682c858e 100644
--- a/drivers/pci/hotplug/shpchp_pci.c
+++ b/drivers/pci/hotplug/shpchp_pci.c
@@ -78,7 +78,6 @@ int shpchp_configure_device(struct slot *p_slot)
 int shpchp_unconfigure_device(struct slot *p_slot)
 {
 	int rc = 0;
-	u8 bctl = 0;
 	struct pci_bus *parent = p_slot->ctrl->pci_dev->subordinate;
 	struct pci_dev *dev, *temp;
 	struct controller *ctrl = p_slot->ctrl;
@@ -93,17 +92,6 @@ int shpchp_unconfigure_device(struct slot *p_slot)
 			continue;
 
 		pci_dev_get(dev);
-		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE) {
-			pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl);
-			if (bctl & PCI_BRIDGE_CTL_VGA) {
-				ctrl_err(ctrl,
-					 "Cannot remove display device %s\n",
-					 pci_name(dev));
-				pci_dev_put(dev);
-				rc = -EINVAL;
-				break;
-			}
-		}
 		pci_stop_and_remove_bus_device(dev);
 		pci_dev_put(dev);
 	}
-- 
2.16.4