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Date: Mon, 12 Oct 2026 17:37:36 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Andreas Hindborg <a.hindborg@kernel.org>
Cc: Miguel Ojeda <ojeda@kernel.org>, Boqun Feng <boqun@kernel.org>,
	Gary Guo <gary@garyguo.net>,
	=?iso-8859-1?Q?Bj=F6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
	Benno Lossin <lossin@kernel.org>, Alice Ryhl <aliceryhl@google.com>,
	Trevor Gross <tmgross@umich.edu>,
	Danilo Krummrich <dakr@kernel.org>,
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	Tamir Duberstein <tamird@kernel.org>,
	Alexandre Courbot <acourbot@nvidia.com>,
	Onur =?iso-8859-1?Q?=D6zkan?= <work@onurozkan.dev>,
	Thomas Gleixner <tglx@kernel.org>, Lorenzo Stoakes <ljs@kernel.org>,
	Vlastimil Babka <vbabka@kernel.org>,
	"Liam R. Howlett" <liam@infradead.org>,
	Uladzislau Rezki <urezki@gmail.com>, linux-kernel@vger.kernel.org,
	rust-for-linux@vger.kernel.org
Subject: Re: [PATCH v3 1/3] rust: add a wrapper for the `num_possible_cpus` C
 function
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On Sat, Oct 03, 2026 at 02:03:57PM +0200, Andreas Hindborg wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
> 
> > On Tue, Sep 29, 2026 at 07:56:48PM +0200, Andreas Hindborg wrote:
> >> This function returns the maximum number of CPUs that can be online.
> >> 
> >> The wrapper is needed by the Rust null block driver.
> >
> > What does it need it for?
> 
> Setting an upper bound on the number of submit and poll queues.

OK I suppose. As long as nobody is going to try and use the return value
as a max for cpuid. That is, num_possible_cpus() <= nr_cpu_ids and all
that.