linux-kernel - Re: remove the nvlink2 pci

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Message-ID: <20210504142236.76994047@bahia.lan>
Date:   Tue, 4 May 2021 14:22:36 +0200
From:   Greg Kurz <groug@...d.org>
To:     Christoph Hellwig <hch@....de>
CC:     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>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>,
        <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 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.

I guess QEMU people should take some action before this percolates
to the QEMU source tree.

Cc'ing relevant QEMU lists to bring the discussion there.

Cheers,

--
Greg

>  drivers/vfio/pci/vfio_pci_nvlink2.c          |  490 ------------------
>  16 files changed, 12 insertions(+), 1511 deletions(-)