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Date: Tue, 17 Feb 2026 17:39:54 +0100
Message-Id: <DGHDW3YKM7L7.C75AZ8DY9K51@kernel.org>
Subject: Re: [PATCH v4 19/33] gpu: nova-core: Hopper/Blackwell: calculate
 reserved FB heap size
Cc: "Alexandre Courbot" <acourbot@nvidia.com>, "Joel Fernandes"
 <joelagnelf@nvidia.com>, "Timur Tabi" <ttabi@nvidia.com>, "Alistair Popple"
 <apopple@nvidia.com>, "Eliot Courtney" <ecourtney@nvidia.com>, "Zhi Wang"
 <zhiw@nvidia.com>, "David Airlie" <airlied@gmail.com>, "Simona Vetter"
 <simona@ffwll.ch>, "Bjorn Helgaas" <bhelgaas@google.com>, "Miguel Ojeda"
 <ojeda@kernel.org>, "Alex Gaynor" <alex.gaynor@gmail.com>, "Boqun Feng"
 <boqun.feng@gmail.com>, "Gary Guo" <gary@garyguo.net>,
 =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, "Benno Lossin"
 <lossin@kernel.org>, "Andreas Hindborg" <a.hindborg@kernel.org>, "Alice
 Ryhl" <aliceryhl@google.com>, "Trevor Gross" <tmgross@umich.edu>,
 <nouveau@lists.freedesktop.org>, <rust-for-linux@vger.kernel.org>, "LKML"
 <linux-kernel@vger.kernel.org>
To: "John Hubbard" <jhubbard@nvidia.com>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <20260210024601.593248-1-jhubbard@nvidia.com>
 <20260210024601.593248-20-jhubbard@nvidia.com>
In-Reply-To: <20260210024601.593248-20-jhubbard@nvidia.com>

On Tue Feb 10, 2026 at 3:45 AM CET, John Hubbard wrote:
> diff --git a/drivers/gpu/nova-core/num.rs b/drivers/gpu/nova-core/num.rs
> index c952a834e662..f068722c5bdf 100644
> --- a/drivers/gpu/nova-core/num.rs
> +++ b/drivers/gpu/nova-core/num.rs
> @@ -215,3 +215,13 @@ pub(crate) const fn [<$from _into_ $into>]<const N: =
$from>() -> $into {
>  impl_const_into!(u64 =3D> { u8, u16, u32 });
>  impl_const_into!(u32 =3D> { u8, u16 });
>  impl_const_into!(u16 =3D> { u8 });
> +
> +/// Aligns `value` up to `ALIGN` at compile time.
> +///
> +/// This is the const-compatible equivalent of [`kernel::ptr::Alignable:=
:align_up`].
> +/// `ALIGN` must be a power of two (enforced at compile time).
> +#[inline(always)]
> +pub(crate) const fn const_align_up<const ALIGN: usize>(value: usize) -> =
usize {

We should probably just add this as a function to Alignable.

> +    build_assert!(ALIGN.is_power_of_two());

ALIGN is a const generic, hence this should be:

	const { core::assert!(ALIGN.is_power_of_two(), "ALIGN must be a power of t=
wo") };

> +    (value + (ALIGN - 1)) & !(ALIGN - 1)
> +}