Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
Date:   Wed, 8 Jun 2022 11:11:11 +0200
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     Javier Martinez Canillas <javierm@redhat.com>
Cc:     Alex Williamson <alex.williamson@redhat.com>,
        maarten.lankhorst@linux.intel.com, mripard@kernel.org,
        tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch,
        kvm@vger.kernel.org, Laszlo Ersek <lersek@redhat.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] Improve vfio-pci primary GPU assignment behavior
Message-ID: <20220608091111.wx2dbboxg2ntuapw@sirius.home.kraxel.org>
References: <165453797543.3592816.6381793341352595461.stgit@omen>
 <badc8e91-f843-2c96-9c02-4fbb59accdc4@redhat.com>
 <20220608074306.wyav3oerq5crdk6c@sirius.home.kraxel.org>
 <b8eee5a7-7428-fcfd-9266-fa63b9fde5e9@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <b8eee5a7-7428-fcfd-9266-fa63b9fde5e9@redhat.com>
Precedence: bulk

  Hi,

> >> But also, this issue isn't something that only affects graphic devices,
> >> right? AFAIU from [1] and [2], the same issue happens if a PCI device
> >> has to be bound to vfio-pci but already was bound to a host driver.
> > 
> > Nope.  There is a standard procedure to bind and unbind pci drivers via
> > sysfs, using /sys/bus/pci/drivers/$name/{bind,unbind}.
> >
> 
> Yes, but the cover letter says:
> 
> "Users often employ kernel command line arguments to disable conflicting
> drivers or perform unbinding in userspace to avoid this"

Thats helpful at times to deal with driver and/or hardware quirks.
Example: Years ago drm drivers used to be horrible when it came to
unbind, leaving oopses and panics left & right when you tried (luckily
it works much better these days).

[ leaving this here for completeness, snipping the remaining reply,
  noting that we are on the same page now ]

thanks & take care,
  Gerd