linux-kernel - Re: [PATCH v2 02/10] gpu: nova-core: Create initial Gsp

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Message-ID: <e99d8012-4fb8-4769-a85e-626653701ac2@nvidia.com>
Date: Wed, 24 Sep 2025 14:15:28 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Lyude Paul <lyude@...hat.com>, Alistair Popple <apopple@...dia.com>,
 rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 dakr@...nel.org, acourbot@...dia.com
Cc: 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>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Joel Fernandes <joelagnelf@...dia.com>, Timur Tabi <ttabi@...dia.com>,
 linux-kernel@...r.kernel.org, nouveau@...ts.freedesktop.org
Subject: Re: [PATCH v2 02/10] gpu: nova-core: Create initial Gsp

On 9/24/25 2:07 PM, Lyude Paul wrote:
> On Wed, 2025-09-24 at 13:50 -0700, John Hubbard wrote:
>> On 9/24/25 1:13 PM, Lyude Paul wrote:
>>> Some comments down below
>> ...
>>>> +/// Creates a self-mapping page table for `obj` at its beginning.
>>>> +fn create_pte_array(obj: &mut CoherentAllocation<u8>) {
>>>> +    let num_pages = obj.size().div_ceil(GSP_PAGE_SIZE);
>>>
>>> Unfortunately there's a bit of a gotcha here - we can't actually use functions
>>> like div_ceil as-is, because a number of 32 bit architectures do not support
>>> u64 / u64 natively. The problem is we don't have __aeabi_uldivmod implemented
>>
>> I recall that we agreed that nova will depend upon CONFIG_64BIT.
>>
>> Does that make this point N/A?
> 
> Oh! I apologize, I must have actually missed that memo :). If we're defending

I do enjoy the "defending" stance, that somehow does feel quite
appropriate at times. :)

> on CONFIG_64BIT then that should be fine:
> 
> Reviewed-by: Lyude Paul <lyude@...hat.com>

I found the memo, here it is for future reference:

https://lore.kernel.org/all/DCHE7FOG5ONY.9SVQATXHGM9M@kernel.org/

thanks,
-- 
John Hubbard