linux-kernel - Re: [PATCH 0/2] Improve vfio-pci primary GPU assignment behavior

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Date:   Wed, 8 Jun 2022 11:11:11 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Javier Martinez Canillas <javierm@...hat.com>
Cc:     Alex Williamson <alex.williamson@...hat.com>,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch,
        kvm@...r.kernel.org, Laszlo Ersek <lersek@...hat.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Improve vfio-pci primary GPU assignment behavior

  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