linux-kernel - [PATCH 7/7] PCI: pciehp: Check that the device is really present before touching it

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Message-Id: <20170926141720.25067-8-mika.westerberg@linux.intel.com>
Date:   Tue, 26 Sep 2017 17:17:20 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     Ashok Raj <ashok.raj@...el.com>,
        Keith Busch <keith.busch@...el.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Lukas Wunner <lukas@...ner.de>,
        Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <yehezkel.bernat@...el.com>,
        Mario.Limonciello@...l.com,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 7/7] PCI: pciehp: Check that the device is really present before touching it

During surprise hot-unplug the device is not there anymore. When that
happens we read 0xffffffff from the registers and pciehp_unconfigure_device()
inadvertently thinks the device is a display device because bridge
control register returns 0xff refusing to remove it:

  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

This causes the hotplug functionality to leave the hierarcy untouched
preventing further hotplug operations.

To fix this verify presence of a device by calling pci_device_is_present()
for it before we touch it any further.

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
---
 drivers/pci/hotplug/pciehp_pci.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/hotplug/pciehp_pci.c b/drivers/pci/hotplug/pciehp_pci.c
index b31702f76149..2a3a62393ba9 100644
--- a/drivers/pci/hotplug/pciehp_pci.c
+++ b/drivers/pci/hotplug/pciehp_pci.c
@@ -101,8 +101,14 @@ int pciehp_unconfigure_device(struct slot *p_slot)
 	 */
 	list_for_each_entry_safe_reverse(dev, temp, &parent->devices,
 					 bus_list) {
+		bool present;
+
 		pci_dev_get(dev);
-		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && presence) {
+
+		/* Check if the device is really there anymore */
+		present = presence ? pci_device_is_present(dev) : false;
+
+		if (dev->hdr_type == PCI_HEADER_TYPE_BRIDGE && present) {
 			pci_read_config_byte(dev, PCI_BRIDGE_CONTROL, &bctl);
 			if (bctl & PCI_BRIDGE_CTL_VGA) {
 				ctrl_err(ctrl,
@@ -113,7 +119,7 @@ int pciehp_unconfigure_device(struct slot *p_slot)
 				break;
 			}
 		}
-		if (!presence) {
+		if (!present) {
 			pci_dev_set_disconnected(dev, NULL);
 			if (pci_has_subordinate(dev))
 				pci_walk_bus(dev->subordinate,
@@ -124,7 +130,7 @@ int pciehp_unconfigure_device(struct slot *p_slot)
 		 * Ensure that no new Requests will be generated from
 		 * the device.
 		 */
-		if (presence) {
+		if (present) {
 			pci_read_config_word(dev, PCI_COMMAND, &command);
 			command &= ~(PCI_COMMAND_MASTER | PCI_COMMAND_SERR);
 			command |= PCI_COMMAND_INTX_DISABLE;
-- 
2.14.1