linux-kernel - Re: [PATCH net RESEND] PCI: fix oops when try to find Root Port for a PCI device

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Date:   Tue, 15 Aug 2017 17:26:02 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     helgaas@...nel.org
Cc:     dingtianhong@...wei.com, leedom@...lsio.com, ashok.raj@...el.com,
        bhelgaas@...gle.com, werner@...lsio.com, ganeshgr@...lsio.com,
        asit.k.mallick@...el.com, patrick.j.cramer@...el.com,
        Suravee.Suthikulpanit@....com, Bob.Shaw@....com,
        l.stach@...gutronix.de, amira@...lanox.com,
        gabriele.paoloni@...wei.com, David.Laight@...lab.com,
        jeffrey.t.kirsher@...el.com, catalin.marinas@....com,
        will.deacon@....com, mark.rutland@....com, robin.murphy@....com,
        alexander.duyck@...il.com, eric.dumazet@...il.com,
        linux-arm-kernel@...ts.infradead.org, netdev@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [PATCH net RESEND] PCI: fix oops when try to find Root Port
 for a PCI device

From: Bjorn Helgaas <helgaas@...nel.org>
Date: Tue, 15 Aug 2017 12:03:31 -0500

> 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.
 ...
> 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

I've integrated all of this feedback and the other Fixes: tag and applied it
to 'net', thanks.