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

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Message-ID: <20251001144814.GB3024065@nvidia.com>
Date: Wed, 1 Oct 2025 11:48:14 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Zhi Wang <zhiw@...dia.com>
Cc: John Hubbard <jhubbard@...dia.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	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 Wed, Oct 01, 2025 at 08:09:37AM +0000, Zhi Wang wrote:
> >> But if the guest sees the passed-through VF as a PF, won't it try to
> >> do things it is not supposed to do like loading the GSP firmware (which
> >> is managed by the host)?
> >
> 
> The guest driver will read PMC_BOOT_1 and check PMC_BOOT_1_VGPU_VF flag 
> to tell if it is running on a VF or a PF.

Yes exactly, and then novacore should modify its behavior and operate
the device in the different mode.

It doesn't matter if a VM is involved or not, a VF driver running side
by side wit the PF driver should still work.

There are use cases where people do this, eg they can stick the VF
into a linux container and use the SRIOV mechanism as a QOS control.
'This container only gets 1/4 of a GPU'

Jason