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Date: Fri, 18 Aug 2017 08:12:51 -0600
From: Alex Williamson <alex.williamson@redhat.com>
To: Jan Glauber <jan.glauber@caviumnetworks.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, david.daney@cavium.com,
        Jon Masters <jcm@redhat.com>,
        Robert Richter <robert.richter@cavium.com>,
        linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 3/3] vfio/pci: Don't probe devices that can't be
 reset
Message-ID: <20170818081251.2bbffe56@w520.home>
In-Reply-To: <20170818134231.GA3464@hc>
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        <20170817070017.1e9c9456@w520.home>
        <20170818134231.GA3464@hc>
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On Fri, 18 Aug 2017 15:42:31 +0200
Jan Glauber <jan.glauber@caviumnetworks.com> wrote:

> On Thu, Aug 17, 2017 at 07:00:17AM -0600, Alex Williamson wrote:
> > On Thu, 17 Aug 2017 10:14:23 +0200
> > Jan Glauber <jglauber@cavium.com> wrote:
> >   
> > > If a PCI device supports neither function-level reset, nor slot
> > > or bus reset then refuse to probe it. A line is printed to inform
> > > the user.  
> > 
> > But that's not what this does, this requires that the device is on a
> > reset-able bus.  This is a massive regression.  With this we could no
> > longer assign devices on the root complex or any device which doesn't
> > return from bus reset and currently makes use of the NO_BUS_RESET flag
> > and works happily otherwise.  Full NAK.  Thanks,  
> 
> Looks like I missed the slot reset check. So how about this:
> 
> if (pci_probe_reset_slot(pdev->slot) && pci_probe_reset_bus(pdev->bus)) {
> 	dev_warn(...);
> 	return -ENODEV;
> }
> 
> Or am I still missing something here?

We don't require that a device is on a reset-able bus/slot, so any
attempt to impose that requirement means that there are devices that
might work perfectly fine that are now excluded from assignment.  The
entire premise is unacceptable.  Thanks,

Alex