linux-kernel - Re: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks

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Message-ID: <20201115170158.GA27152@wunner.de>
Date:   Sun, 15 Nov 2020 18:01:58 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     "Eric W. Biederman" <ebiederm@...ssion.com>,
        Bjorn Helgaas <helgaas@...nel.org>, linux-pci@...r.kernel.org,
        kernelfans@...il.com, andi@...stfloor.org, hpa@...or.com,
        bhe@...hat.com, x86@...nel.org, okaya@...nel.org, mingo@...hat.com,
        jay.vosburgh@...onical.com, dyoung@...hat.com,
        gavin.guo@...onical.com,
        "Guilherme G. Piccoli" <gpiccoli@...onical.com>, bp@...en8.de,
        bhelgaas@...gle.com, shan.gavin@...ux.alibaba.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>, kernel@...ccoli.net,
        kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
        ddstreet@...onical.com, vgoyal@...hat.com
Subject: Re: [PATCH 1/3] x86/quirks: Scan all busses for early PCI quirks

On Sun, Nov 15, 2020 at 04:11:43PM +0100, Thomas Gleixner wrote:
> Unfortunately there is no way to tell the APIC "Mask vector X" and the
> dump kernel does neither know which device it comes from nor does it
> have enumerated PCI completely which would reset the device and shutup
> the spew. Due to the interrupt storm it does not get that far.

Can't we just set DisINTx, clear MSI Enable and clear MSI-X Enable
on all active PCI devices in the crashing kernel before starting the
crash kernel?  So that the crash kernel starts with a clean slate?

Guilherme's original patches from 2018 iterate over all 256 PCI buses.
That might impact boot time negatively.  The reason he has to do that
is because the crashing kernel doesn't know which devices exist and
which have interrupts enabled.  However the crashing kernel has that
information.  It should either disable interrupts itself or pass the
necessary information to the crashing kernel as setup_data or whatever.

Guilherme's patches add a "clearmsi" command line parameter.  I guess
the idea is that the parameter is always passed to the crash kernel
but the patches don't do that, which seems odd.

Thanks,

Lukas