linux-kernel - Re: [PATCH] PCI: Add link_change error handler and vfio-pci user

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Date:   Mon, 29 Apr 2019 10:59:26 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Sinan Kaya <Okaya@...nel.org>
Cc:     Bjorn Helgaas <helgaas@...nel.org>, mr.nuke.me@...il.com,
        linux-pci@...r.kernel.org, austin_bolen@...l.com,
        alex_gagniuc@...lteam.com, keith.busch@...el.com,
        Shyam_Iyer@...l.com, lukas@...ner.de,
        torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Add link_change error handler and vfio-pci user

On Mon, 29 Apr 2019 09:45:28 -0700
Sinan Kaya <Okaya@...nel.org> wrote:

> On 4/29/2019 10:51 AM, Alex Williamson wrote:
> > So where do we go from here?  I agree that dmesg is not necessarily a
> > great choice for these sorts of events and if they went somewhere else,
> > maybe I wouldn't have the same concerns about them generating user
> > confusion or contributing to DoS vectors from userspace drivers.  As it
> > is though, we have known cases where benign events generate confusing
> > logging messages, which seems like a regression.  Drivers didn't ask
> > for a link_change handler, but nor did they ask that the link state to
> > their device be monitored so closely.  Maybe this not only needs some
> > sort of change to the logging mechanism, but also an opt-in by the
> > driver if they don't expect runtime link changes.  Thanks,  
> 
> Is there anyway to detect autonomous hardware management support and
> not report link state changes in that situation?
> 
> I thought there were some capability bits for these.

Not that we can find, this doesn't trigger the separate autonomous
bandwidth notification interrupt.  Thanks,

Alex