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Date: Tue, 17 Feb 2026 21:04:42 +0100
Message-Id: <DGHI8WRKBQS9.38910L6FIIZTE@kernel.org>
Subject: Re: [PATCH v4 25/33] gpu: nova-core: Hopper/Blackwell: larger
 non-WPR heap
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>
 <20260210024601.593248-26-jhubbard@nvidia.com>
In-Reply-To: <20260210024601.593248-26-jhubbard@nvidia.com>

On Tue Feb 10, 2026 at 3:45 AM CET, John Hubbard wrote:
> Hopper, Blackwell and later require more space for the non-WPR heap.
>
> Add a new FbHal method to return the non-WPR heap size, and create a new
> GH100 HAL for Hopper and GB100 HAL for Blackwell that return the
> appropriate value for each GPU architecture.
>
> Cc: Timur Tabi <ttabi@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---
>  drivers/gpu/nova-core/fb.rs           | 14 +++++++---
>  drivers/gpu/nova-core/fb/hal.rs       |  7 +++--
>  drivers/gpu/nova-core/fb/hal/ga102.rs |  2 +-
>  drivers/gpu/nova-core/fb/hal/gb100.rs | 37 +++++++++++++++++++++++++++
>  drivers/gpu/nova-core/fb/hal/gh100.rs | 37 +++++++++++++++++++++++++++
>  5 files changed, 91 insertions(+), 6 deletions(-)
>  create mode 100644 drivers/gpu/nova-core/fb/hal/gb100.rs
>  create mode 100644 drivers/gpu/nova-core/fb/hal/gh100.rs
>
> diff --git a/drivers/gpu/nova-core/fb.rs b/drivers/gpu/nova-core/fb.rs
> index 3a2b79a5c107..7c502f15622c 100644
> --- a/drivers/gpu/nova-core/fb.rs
> +++ b/drivers/gpu/nova-core/fb.rs
> @@ -98,6 +98,15 @@ pub(crate) fn unregister(&self, bar: &Bar0) {
>      }
>  }
> =20
> +/// Calculate non-WPR heap size based on chipset architecture.
> +/// This matches the logic used in FSP for consistency.
> +pub(crate) fn calc_non_wpr_heap_size(chipset: Chipset) -> u64 {
> +    hal::fb_hal(chipset)
> +        .non_wpr_heap_size()
> +        .map(u64::from)
> +        .unwrap_or(SZ_1M as u64)

This should use u64::from_safe_cast().

Also, I already brought this up in the context of GPU buddy, I wonder if we
should just add SZ_* constants for 64-bit devices. Shouldn't be too hard to
generate the corresponding code.

I think it is a repeating pattern, and having to use u64::from_safe_cast() =
all
the time seems cumbersome.