linux-kernel - Re: [PATCH] gpu: nova-core: fix aux device registration for multi-GPU systems

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Message-ID: <aYSfpf3xZNwZhzXs@casper.infradead.org>
Date: Thu, 5 Feb 2026 13:48:21 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Gary Guo <gary@...yguo.net>
Cc: John Hubbard <jhubbard@...dia.com>, Danilo Krummrich <dakr@...nel.org>,
	Alexandre Courbot <acourbot@...dia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Timur Tabi <ttabi@...dia.com>, Alistair Popple <apopple@...dia.com>,
	Eliot Courtney <ecourtney@...dia.com>, Zhi Wang <zhiw@...dia.com>,
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	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, rust-for-linux@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] gpu: nova-core: fix aux device registration for
 multi-GPU systems

On Thu, Feb 05, 2026 at 01:44:27PM +0000, Gary Guo wrote:
> > Fix this by using an atomic counter to generate unique IDs for each
> > GPU's aux device registration. The TODO item to eventually use XArray
> > for recycling aux device IDs is retained, but for now, this works very
> > nicely.
> >
> > This has the side effect of making debugfs[1] work on multi-GPU systems.
> 
> Hi John,
> 
> Looks like this is something that should be achieved via IDA?

Yes, if you have no need to go from ID to pointer, an IDA is better.
That said, as far as I understand what this code is doing, an atomic_t
solves the problem just fine and is cheaper.