linux-kernel - [PATCH AUTOSEL for 3.18 30/40] PCI: Avoid bus reset if bridge itself is broken

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Date:   Wed, 13 Dec 2017 01:59:18 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     David Daney <david.daney@...ium.com>,
        Jan Glauber <jglauber@...ium.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 3.18 30/40] PCI: Avoid bus reset if bridge itself
 is broken

From: David Daney <david.daney@...ium.com>

[ Upstream commit 357027786f3523d26f42391aa4c075b8495e5d28 ]

When checking to see if a PCI bus can safely be reset, we previously
checked to see if any of the children had their PCI_DEV_FLAGS_NO_BUS_RESET
flag set.  Children marked with that flag are known not to behave well
after a bus reset.

Some PCIe root port bridges also do not behave well after a bus reset,
sometimes causing the devices behind the bridge to become unusable.

Add a check for PCI_DEV_FLAGS_NO_BUS_RESET being set in the bridge device
to allow these bridges to be flagged, and prevent their secondary buses
from being reset.

Signed-off-by: David Daney <david.daney@...ium.com>
[jglauber@...ium.com: fixed typo]
Signed-off-by: Jan Glauber <jglauber@...ium.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
Reviewed-by: Alex Williamson <alex.williamson@...hat.com>

Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/pci/pci.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index d3decb52eb7e..1563cfadeaef 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3580,6 +3580,10 @@ static bool pci_bus_resetable(struct pci_bus *bus)
 {
 	struct pci_dev *dev;
 
+
+	if (bus->self && (bus->self->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET))
+		return false;
+
 	list_for_each_entry(dev, &bus->devices, bus_list) {
 		if (dev->dev_flags & PCI_DEV_FLAGS_NO_BUS_RESET ||
 		    (dev->subordinate && !pci_bus_resetable(dev->subordinate)))
-- 
2.11.0