Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Tue, 4 May 2021 15:08:51 +0200
From:   Cornelia Huck <cohuck@redhat.com>
To:     Christoph Hellwig <hch@lst.de>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        qemu-devel@nongnu.org, Daniel Vetter <daniel@ffwll.ch>,
        kvm@vger.kernel.org, David Airlie <airlied@linux.ie>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Greg Kurz <groug@kaod.org>, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org,
        Alex Williamson <alex.williamson@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        Jason Gunthorpe <jgg@nvidia.com>, linux-api@vger.kernel.org,
        qemu-ppc@nongnu.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: remove the nvlink2 pci_vfio subdriver v2
Message-ID: <20210504150851.54e278f8.cohuck@redhat.com>
In-Reply-To: <20210504130039.GA7711@lst.de>
References: <20210326061311.1497642-1-hch@lst.de>
        <20210504142236.76994047@bahia.lan>
        <YJFFG1tSP0dUCxcX@kroah.com>
        <20210504130039.GA7711@lst.de>
Organization: Red Hat GmbH
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Precedence: bulk

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