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Date:   Mon, 1 Feb 2021 14:35:58 -0400
From:   Jason Gunthorpe <jgg@nvidia.com>
To:     Max Gurtovoy <mgurtovoy@nvidia.com>
CC:     <cohuck@redhat.com>, <kvm@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <alex.williamson@redhat.com>,
        <liranl@nvidia.com>, <oren@nvidia.com>, <tzahio@nvidia.com>,
        <leonro@nvidia.com>, <yarong@nvidia.com>, <aviadye@nvidia.com>,
        <shahafs@nvidia.com>, <artemp@nvidia.com>, <kwankhede@nvidia.com>,
        <ACurrid@nvidia.com>, <gmataev@nvidia.com>, <cjia@nvidia.com>,
        <mjrosato@linux.ibm.com>, <yishaih@nvidia.com>, <aik@ozlabs.ru>
Subject: Re: [PATCH 9/9] vfio/pci: use powernv naming instead of nvlink2
Message-ID: <20210201183558.GM4247@nvidia.com>
References: <20210201162828.5938-1-mgurtovoy@nvidia.com>
 <20210201162828.5938-10-mgurtovoy@nvidia.com>
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On Mon, Feb 01, 2021 at 04:28:28PM +0000, Max Gurtovoy wrote:
> This patch doesn't change any logic but only align to the concept of
> vfio_pci_core extensions. Extensions that are related to a platform
> and not to a specific vendor of PCI devices should be part of the
> core driver. Extensions that are specific for PCI device vendor should go
> to a dedicated vendor vfio-pci driver.
> 
> For now, powernv extensions will include only nvlink2.
> 
> Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
>  drivers/vfio/pci/Kconfig                                    | 6 ++++--
>  drivers/vfio/pci/Makefile                                   | 2 +-
>  drivers/vfio/pci/vfio_pci_core.c                            | 4 ++--
>  drivers/vfio/pci/{vfio_pci_nvlink2.c => vfio_pci_powernv.c} | 0
>  drivers/vfio/pci/vfio_pci_private.h                         | 2 +-
>  5 files changed, 8 insertions(+), 6 deletions(-)
>  rename drivers/vfio/pci/{vfio_pci_nvlink2.c => vfio_pci_powernv.c} (100%)

This is really nothing to do with PPC, "nvlink" is a PCI device that
shows the entire GPU memory space on these special power systems, and
the this driver changes the normal vfio-pci behavior to match the
single device.

This is probably the best existing example of something that could be
a vendor PCI driver because of how single-device specific it really
is.

Read 7f92891778dff62303c070ac81de7b7d80de331a to get some sense of how
very special a device it is.

This could be like mlx5, with the single PCI ID pre-populated in a
match table.

That is probably the key test for vfio_pci_core vs vfio_pci - if the
modification is triggered by a single PCI ID that can be matched it is
vfio_pci side, not core.  Compared to the s390 stuff which applies to
all PCI devices in the system.

Jason