linux-kernel - Re: [PATCH drm-next v5 00/14] [RFC] DRM GPUVA Manager & Nouveau VM

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Message-ID: <CAPM=9tyv5Fje0iL0-2oJQBKEsg-nc-YV9q4BSg5SwnBvGvrzDw@mail.gmail.com>
Date:   Tue, 20 Jun 2023 17:13:31 +1000
From:   Dave Airlie <airlied@...il.com>
To:     Oded Gabbay <ogabbay@...nel.org>
Cc:     Danilo Krummrich <dakr@...hat.com>,
        Donald Robson <Donald.Robson@...tec.com>, daniel@...ll.ch,
        tzimmermann@...e.de, mripard@...nel.org, corbet@....net,
        christian.koenig@....com, bskeggs@...hat.com,
        Liam.Howlett@...cle.com, matthew.brost@...el.com,
        boris.brezillon@...labora.com, alexdeucher@...il.com,
        bagasdotme@...il.com, willy@...radead.org, jason@...kstrand.net,
        dri-devel@...ts.freedesktop.org, nouveau@...ts.freedesktop.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-next v5 00/14] [RFC] DRM GPUVA Manager & Nouveau
 VM_BIND UAPI

On Tue, 20 Jun 2023 at 17:06, Oded Gabbay <ogabbay@...nel.org> wrote:
>
> On Tue, Jun 20, 2023 at 7:05 AM Dave Airlie <airlied@...il.com> wrote:
> >
> > Since this is feature is nouveau only currently and doesn't disturb
> > the current nouveau code paths, I'd like to try and get this work in
> > tree so other drivers can work from it.
> >
> > If there are any major objections to this, I'm happy to pull it back
> > out again, but I'd like to get some acks/rb in the next couple of days
> > in order to land some of it.
> >
> > Dave.
> >
> >
> > >
> > > forgot to add your email address to the patch series - sorry about that.
> > >
> > > This series (v5) contains the Documentation changes you requested.
> > >
> > > - Danilo
> > >
> > > On 6/20/23 02:42, Danilo Krummrich wrote:
> > > > This patch series provides a new UAPI for the Nouveau driver in order to
> > > > support Vulkan features, such as sparse bindings and sparse residency.
> > > >
> > > > Furthermore, with the DRM GPUVA manager it provides a new DRM core feature to
> > > > keep track of GPU virtual address (VA) mappings in a more generic way.
> > > >
> > > > The DRM GPUVA manager is indented to help drivers implement userspace-manageable
> > > > GPU VA spaces in reference to the Vulkan API. In order to achieve this goal it
> > > > serves the following purposes in this context.
> > > >
> > > >      1) Provide infrastructure to track GPU VA allocations and mappings,
> > > >         making use of the maple_tree.
> > > >
> > > >      2) Generically connect GPU VA mappings to their backing buffers, in
> > > >         particular DRM GEM objects.
> Will this manager be able to connect GPU VA mappings to host memory
> allocations (aka user pointers) ?
>
> I only skimmed over the uapi definitions, but from that quick glance I
> saw you can only pass a (gem) handle to the vm bind uapi.
>
> I think it is an important feature because you don't want to have two
> GPU VA managers running in your driver (if that's even possible).
> Maybe we should at least try to make sure the uapi is/will be
> compatible with such an extension.
>

I think that would have to be a new uAPI entry point anyways, since
managing user ptrs is extra, but the uAPI is nouveau specific and
nouveau has no hostptr support as of now.

The gpuva manager is kernel internal, I think adding host ptr tracking
is useful, but I don't think it's a blocker right now.

One of the reasons I'd like to get this in the tree is to add things
like that instead of overloading this initial patchset with feature
creep.

Dave.