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Date: Tue, 4 May 2021 14:59:07 +0200
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Greg Kurz <groug@kaod.org>
Subject: Re: remove the nvlink2 pci_vfio subdriver v2
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References: <20210326061311.1497642-1-hch@lst.de>
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Cc: Daniel Vetter <daniel@ffwll.ch>, kvm@vger.kernel.org,
 David Airlie <airlied@linux.ie>, linux-kernel@vger.kernel.org,
 dri-devel@lists.freedesktop.org, qemu-devel@nongnu.org,
 Alex Williamson <alex.williamson@redhat.com>,
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 linux-api@vger.kernel.org, qemu-ppc@nongnu.org, linuxppc-dev@lists.ozlabs.org,
 Christoph Hellwig <hch@lst.de>
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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@lst.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