linux-kernel - Re: [PATCH 2/2] pci: Don't set RCB bit in LNKCTL if the upstream bridge hasn't

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Date:   Mon, 14 Nov 2016 11:16:51 -0500
From:   Don Dutile <ddutile@...hat.com>
To:     Johannes Thumshirn <jthumshirn@...e.de>,
        Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Alexander Graf <agraf@...e.de>,
        Hannes Reinecke <hare@...e.de>
Subject: Re: [PATCH 2/2] pci: Don't set RCB bit in LNKCTL if the upstream
 bridge hasn't

On 11/14/2016 06:56 AM, Johannes Thumshirn wrote:
> On Wed, Nov 09, 2016 at 11:11:40AM -0600, Bjorn Helgaas wrote:
>> Hi Johannes,
>>
>> On Wed, Nov 02, 2016 at 04:35:52PM -0600, Johannes Thumshirn wrote:
>>> The Read Completion Boundary (RCB) bit must only be set on a device or
>>> endpoint if it is set on the root complex.
>>>
>>> Certain BIOSes erroneously set the RCB Bit in their ACPI _HPX Tables
>>> even if it is not set on the root port. This is a violation to the PCIe
>>> Specification and is known to bring some Mellanox Connect-X 3 HCAs into
>>> a state where they can't map their firmware and go into error recovery.
>>>
>>> BIOS Information
>>> 	Vendor: IBM
>>> 	Version: -[A8E120CUS-1.30]-
>>> 	Release Date: 08/22/2016
>>
>> This seems like a pretty serious problem (sounds like maybe the HCA is
>> completely useless?)
>
> Correct.
>
>>
>> Can you point us at a bugzilla or other problem report?  It's nice to
>> have details of what this looks like to a user, so people who trip
>> over this problem have a little more chance of finding the solution.
>
> As we already said, our bugzilla entry for this is not accessible from the
> outside, but I know Red Hat does have a bugzilla entry for the same issue as
> well. Maybe this is reachable from the outside (adding Don for this, as I know
> he has worked on this problem as well).
>
RHEL bz's are not accessible from the outside.
I suggest capturing the content of the RH bz issue and creating a k.o. bz
with the information.

>>
>> 7a1562d4f2d0 ("PCI: Apply _HPX Link Control settings to all devices
>> with a link") appeared in v3.18, so it's probably not a *new* problem,
>> so my guess is that this is v4.10 material.
>
> Yes 4.10 sounds good to me. I personally think, this problem hasn't
> materialized yet, as this is the kind of hardware you run on a rather /stable/
> kernel either you built on your own or get from an enterprise distribution and
> until recently these kernels haven't been updated to something newer than
> 3.18.
>
> Thanks,
> 	Johannes
>