Re: [PATCH v12.1 1/1] rust: gpu: Add GPU buddy allocator bindings

["Alexandre Courbot" <acourbot@nvidia.com>]

On Tue Mar 17, 2026 at 10:10 AM JST, John Hubbard wrote:
> On 3/16/26 6:02 PM, Alexandre Courbot wrote:
>> On Tue Mar 17, 2026 at 3:51 AM JST, John Hubbard wrote:
>>> On 3/16/26 6:12 AM, Alexandre Courbot wrote:
>>>> On Mon Mar 9, 2026 at 10:53 PM JST, Joel Fernandes wrote:
>>> ...
>>>> I'm a bit torn as to whether we should use a `u64` to conform with the C
>>>> API, but doing so would mean we cannot use an `Alignment`...
>>>
>>> Alex, have you seen my Alignment patch [1], for that? It's sitting 
>>> around with only Miguel having responded, but seems like exactly
>>> what you're talking about here.
>> 
>> Not exactly - this patch provides a shortcut for creating an Alignment
>> from a u64, but it doesn't allow to store alignments larger than 4GB on
>> a 32-bit architecture since the value itself is still stored as a `usize`.
>> 
>> But that's really a theoretical worry of mine anyway - nobody will ever
>> work with buffers larger than 4GB on a 32-bit arch to begin with.
>
> Actually, in the CPU world, this claim was made early and often, but
> turned out to be wildly wrong! That's why we have "high mem" in
> linux-mm (a constant source of suffering for kernel devs).
>
> The 32-bit systems designer do not feel constrained to keep their
> memory sizes below that which they can directly address. :)

Yet IIUC PAE still limits a single process to a 4GB address space (and
`usize` is still 32-bit anyway), so hopefully we will be spared that
pain. :)