linux-kernel - Re: remove the nvlink2 pci

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Date:   Tue, 4 May 2021 14:59:07 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Greg Kurz <groug@...d.org>
Cc:     Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jason Gunthorpe <jgg@...dia.com>, kvm@...r.kernel.org,
        David Airlie <airlied@...ux.ie>, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, Paul Mackerras <paulus@...ba.org>,
        Daniel Vetter <daniel@...ll.ch>, linux-api@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, qemu-devel@...gnu.org,
        qemu-ppc@...gnu.org
Subject: Re: remove the nvlink2 pci_vfio subdriver v2

On Tue, May 04, 2021 at 02:22:36PM +0200, Greg Kurz wrote:
> On Fri, 26 Mar 2021 07:13:09 +0100
> Christoph Hellwig <hch@....de> wrote:
> 
> > Hi all,
> > 
> > the nvlink2 vfio subdriver is a weird beast.  It supports a hardware
> > feature without any open source component - what would normally be
> > the normal open source userspace that we require for kernel drivers,
> > although in this particular case user space could of course be a
> > kernel driver in a VM.  It also happens to be a complete mess that
> > does not properly bind to PCI IDs, is hacked into the vfio_pci driver
> > and also pulles in over 1000 lines of code always build into powerpc
> > kernels that have Power NV support enabled.  Because of all these
> > issues and the lack of breaking userspace when it is removed I think
> > the best idea is to simply kill.
> > 
> > Changes since v1:
> >  - document the removed subtypes as reserved
> >  - add the ACK from Greg
> > 
> > Diffstat:
> >  arch/powerpc/platforms/powernv/npu-dma.c     |  705 ---------------------------
> >  b/arch/powerpc/include/asm/opal.h            |    3 
> >  b/arch/powerpc/include/asm/pci-bridge.h      |    1 
> >  b/arch/powerpc/include/asm/pci.h             |    7 
> >  b/arch/powerpc/platforms/powernv/Makefile    |    2 
> >  b/arch/powerpc/platforms/powernv/opal-call.c |    2 
> >  b/arch/powerpc/platforms/powernv/pci-ioda.c  |  185 -------
> >  b/arch/powerpc/platforms/powernv/pci.c       |   11 
> >  b/arch/powerpc/platforms/powernv/pci.h       |   17 
> >  b/arch/powerpc/platforms/pseries/pci.c       |   23 
> >  b/drivers/vfio/pci/Kconfig                   |    6 
> >  b/drivers/vfio/pci/Makefile                  |    1 
> >  b/drivers/vfio/pci/vfio_pci.c                |   18 
> >  b/drivers/vfio/pci/vfio_pci_private.h        |   14 
> >  b/include/uapi/linux/vfio.h                  |   38 -
> 
> 
> Hi Christoph,
> 
> FYI, these uapi changes break build of QEMU.

What uapi changes?

What exactly breaks?

Why does QEMU require kernel driver stuff?

thanks,

greg k-h