Re: [PATCH net RESEND] PCI: fix oops when try to find Root Port for a PCI device
From: Bjorn Helgaas <helgaas@kernel.org>
Date: 2017-08-15 17:03:35
Also in:
linux-arm-kernel, linux-pci, lkml
Subsystem:
pci subsystem, the rest · Maintainers:
Bjorn Helgaas, Linus Torvalds
On Tue, Aug 15, 2017 at 11:24:48PM +0800, Ding Tianhong wrote:
Eric report a oops when booting the system after applying
the commit a99b646afa8a ("PCI: Disable PCIe Relaxed..."):
...It looks like the pci_find_pcie_root_port() was trying to find the Root Port for the PCI device which is the Root Port already, it will return NULL and trigger the problem, so check the highest_pcie_bridge to fix thie problem.
The problem was actually with a Root Complex Integrated Endpoint that
has no upstream PCIe device:
00:05.2 System peripheral: Intel Corporation Device 0e2a (rev 04)
Subsystem: Intel Corporation Device 0e2a
Control: I/O- Mem- BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- DisINTx-
Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
Capabilities: [40] Express (v2) Root Complex Integrated Endpoint, MSI 00
DevCap: MaxPayload 128 bytes, PhantFunc 0, Latency L0s <64ns, L1 <1us
ExtTag- RBE- FLReset-
DevCtl: Report errors: Correctable- Non-Fatal- Fatal+ Unsupported+
RlxdOrd+ ExtTag- PhantFunc- AuxPwr- NoSnoop+
MaxPayload 128 bytes, MaxReadReq 128 bytes
Fixes: a99b646afa8a ("PCI: Disable PCIe Relaxed Ordering if unsupported")
This also
Fixes: c56d4450eb68 ("PCI: Turn off Request Attributes to avoid Chelsio T5 Completion erratum")
which added pci_find_pcie_root_port(). Prior to this Relaxed Ordering
series, we only used pci_find_pcie_root_port() in a Chelsio quirk that
only applied to non-integrated endpoints, so we didn't trip over the
bug.
quoted hunk ↗ jump to hunk
Reported-by: Eric Dumazet <redacted> Signed-off-by: Eric Dumazet <redacted> Signed-off-by: Ding Tianhong <redacted> --- drivers/pci/pci.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index af0cc34..7e2022f 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c@@ -522,7 +522,8 @@ struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev) bridge = pci_upstream_bridge(bridge); } - if (pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT) + if (highest_pcie_bridge && + pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT) return NULL; return highest_pcie_bridge;--
I think structuring the fix as follows is a little more readable:
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index af0cc3456dc1..587cd7623ed8 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c@@ -522,10 +522,11 @@ struct pci_dev *pci_find_pcie_root_port(struct pci_dev *dev) bridge = pci_upstream_bridge(bridge); } - if (pci_pcie_type(highest_pcie_bridge) != PCI_EXP_TYPE_ROOT_PORT) - return NULL; + if (highest_pcie_bridge && + pci_pcie_type(highest_pcie_bridge) == PCI_EXP_TYPE_ROOT_PORT) + return highest_pcie_bridge; - return highest_pcie_bridge; + return NULL; } EXPORT_SYMBOL(pci_find_pcie_root_port);