linux-kernel - Re: [RFC PATCH] PCI, kdump: Clear bus master bit upon shutdown in kdump kernel

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Message-ID: <20200224045618.GA16543@dhcp-128-65.nay.redhat.com>
Date:   Mon, 24 Feb 2020 12:56:18 +0800
From:   Dave Young <dyoung@...hat.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Kairui Song <kasong@...hat.com>, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, kexec@...ts.infradead.org,
        Jerry Hoemann <jerry.hoemann@....com>,
        Baoquan He <bhe@...hat.com>,
        Khalid Aziz <khalid@...ehiking.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Randy Wright <rwright@....com>,
        Myron Stowe <myron.stowe@...hat.com>
Subject: Re: [RFC PATCH] PCI, kdump: Clear bus master bit upon shutdown in
 kdump kernel

Hi Bjorn,
On 02/22/20 at 10:56am, Bjorn Helgaas wrote:
> [+cc Khalid, Deepa, Randy, Dave, Myron]
> 
> On Thu, Dec 26, 2019 at 03:21:18AM +0800, Kairui Song wrote:
> > There are reports about kdump hang upon reboot on some HPE machines,
> > kernel hanged when trying to shutdown a PCIe port, an uncorrectable
> > error occurred and crashed the system.
> 
> Did we ever make progress on this?  This definitely sounds like a
> problem that needs to be fixed, but I don't see a resolution here.
> 

I'm not familar with the PCI details,  but if this only adds a quirk for
kdump use and no other risks added then it should be good to have.

Or we can provide a kernel parameter for the quirk?  Then it is even
limited to only be effective when in-kdump && the-param-is-used

Anyway still prefer to people who know more about this area to evaluate
the risk.

Thanks
Dave