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Message-ID: <ZO9imcoN5l28GE9+@nvidia.com>
Date: Wed, 30 Aug 2023 12:39:05 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: ankita@...dia.com, alex.williamson@...hat.com, yishaih@...dia.com,
shameerali.kolothum.thodi@...wei.com, kevin.tian@...el.com,
aniketa@...dia.com, cjia@...dia.com, kwankhede@...dia.com,
targupta@...dia.com, vsethi@...dia.com, acurrid@...dia.com,
apopple@...dia.com, jhubbard@...dia.com, danw@...dia.com,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
David Airlie <airlied@...hat.com>,
dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH v7 1/1] vfio/nvgpu: Add vfio pci variant module for grace
hopper
On Wed, Aug 30, 2023 at 06:50:32AM -0700, Christoph Hellwig wrote:
> I know I'm chiming in a bit late, but what ultimate user space is going
> to use this? We should not add anything to the kernel that can't
> be used without fully open user space.
qemu will get the matching VFIO userspace patches, I think they were
posted someplace already.
> vfio has traditionally been a bit special as it "just" passes devices
> through, so any user space could just be a user space driver for a
> random device on $FOO bus, including an actual Linux driver in a VM,
> but this driver has very specific semantics for a very specific piece
> of hardware, so it really needs to be treated like a generic GPU driver
> or accelerator driver.
This is basically a pre-CXL driver. It takes a PCI device and some
non-standard CXL-ish metadata and adapts it to VFIO.
In a post-CXL world this same functionality of managing the 'cache
coherent BAR' for VFIO would be done generically by some generic
vfio-cxl driver.
Jason
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