linux-kernel - Re: [PATCH 0/2] rust: pci: expose is_virtfn() and reject VFs in nova-core

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Message-ID: <643653d4-5074-473b-81eb-149110e9bced@nvidia.com>
Date: Wed, 1 Oct 2025 18:50:37 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Alexandre Courbot <acourbot@...dia.com>, Zhi Wang <zhiw@...dia.com>,
 Jason Gunthorpe <jgg@...dia.com>
Cc: Danilo Krummrich <dakr@...nel.org>, Joel Fernandes
 <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>,
 Alistair Popple <apopple@...dia.com>, Surath Mitra <smitra@...dia.com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <lossin@...nel.org>, Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
 "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
 "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
 "rust-for-linux@...r.kernel.org" <rust-for-linux@...r.kernel.org>,
 LKML <linux-kernel@...r.kernel.org>,
 Alex Williamson <alex.williamson@...hat.com>
Subject: Re: [PATCH 0/2] rust: pci: expose is_virtfn() and reject VFs in
 nova-core

On 10/1/25 6:43 PM, Alexandre Courbot wrote:
> On Thu Oct 2, 2025 at 6:13 AM JST, Zhi Wang wrote:
>> On 1.10.2025 17.48, Jason Gunthorpe wrote:
>>> On Wed, Oct 01, 2025 at 08:09:37AM +0000, Zhi Wang wrote:
...
>> Right, I also mentioned the same use cases of NIC/GPU in another reply
>> to Danilo. But what I get is NVIDIA doesn't use bare metal VF to support
>> linux container, it seems there have been other solutions. IMHO, it is
>> not mandatory that we have to support VF driver on bare metal so far
>> yet.
> 
> For my education, what gets in the way of supporting a VF on the bare
> metal if we already support it from inside a VM?

Synthesizing a response from what I've learned here:

First of all, the PF and VFs will probe() nova-core with the same 
device ID, so nova-core will get multiple probe() calls for the
same device. That has to be handled. (Thanks to Joel for pointing
that out.)

Next, for actual true VF support, nova-core will need to "provision"
the VFs, which I have learned involves the following:

    * allocate vidmem (or "VRAM" in DRM terminology)
    * set up compute quotas
    * configure which GPU features are exposed


thanks,
-- 
John Hubbard