linux-kernel - Re: remove the nvlink2 pci

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Date:   Tue, 4 May 2021 15:08:51 +0200
From:   Cornelia Huck <cohuck@...hat.com>
To:     Christoph Hellwig <hch@....de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        qemu-devel@...gnu.org, Daniel Vetter <daniel@...ll.ch>,
        kvm@...r.kernel.org, David Airlie <airlied@...ux.ie>,
        Michael Ellerman <mpe@...erman.id.au>,
        Greg Kurz <groug@...d.org>, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org,
        Alex Williamson <alex.williamson@...hat.com>,
        Paul Mackerras <paulus@...ba.org>,
        Jason Gunthorpe <jgg@...dia.com>, linux-api@...r.kernel.org,
        qemu-ppc@...gnu.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: remove the nvlink2 pci_vfio subdriver v2

On Tue, 4 May 2021 15:00:39 +0200
Christoph Hellwig <hch@....de> wrote:

> On Tue, May 04, 2021 at 02:59:07PM +0200, Greg Kroah-Hartman wrote:
> > > Hi Christoph,
> > > 
> > > FYI, these uapi changes break build of QEMU.  
> > 
> > What uapi changes?
> > 
> > What exactly breaks?
> > 
> > Why does QEMU require kernel driver stuff?  
> 
> Looks like it pull in the uapi struct definitions unconditionally
> instead of having a local copy.  We could fix that by just putting
> them back, but to me this seems like a rather broken configuration
> in qemu when it pulls in headers from the running/installed kernel
> without any feature checks before using them.
> 

It is not pulling them from the installed kernel, but from a
development version to get new definitions. Removing things in the
kernel requires workarounds in QEMU until it can remove those things as
well. It is not a dumb update...