Re: [PATCH v3 02/11] gpu: nova-core: move GSP boot code out of `Gpu` constructor

["Danilo Krummrich" <dakr@kernel.org>]

On Tue Sep 2, 2025 at 4:31 PM CEST, Alexandre Courbot wrote:
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 274989ea1fb4a5e3e6678a08920ddc76d2809ab2..1062014c0a488e959379f009c2e8029ffaa1e2f8 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -6,6 +6,8 @@
>  
>  #[pin_data]
>  pub(crate) struct NovaCore {
> +    // Placeholder for the real `Gsp` object once it is built.
> +    pub(crate) gsp: (),
>      #[pin]
>      pub(crate) gpu: Gpu,
>      _reg: auxiliary::Registration,
> @@ -40,8 +42,14 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> Result<Pin<KBox<Self
>          )?;
>  
>          let this = KBox::pin_init(
> -            try_pin_init!(Self {
> +            try_pin_init!(&this in Self {
>                  gpu <- Gpu::new(pdev, bar)?,
> +                gsp <- {
> +                    // SAFETY: `this.gpu` is initialized to a valid value.
> +                    let gpu = unsafe { &(*this.as_ptr()).gpu };
> +
> +                    gpu.start_gsp(pdev)?
> +                },

Please use pin_chain() [1] for this.

More in general, unsafe code should be the absolute last resort. If we add new
unsafe code I'd love to see a comment justifying why there's no other way than
using unsafe code for this, as we agreed in [2].

I did a quick grep on this series and I see 21 occurrences of "unsafe", if I
substract the ones for annotations and for FromBytes impls, it's still 9 new
ones. :(

Do we really need all of them?

Otherwise, I really like this, it's a great improvement over initializing
everything into the Gpu struct -- thanks for the refactoring!

[1] https://rust.docs.kernel.org/kernel/prelude/trait.PinInit.html#method.pin_chain
[2] https://docs.kernel.org/gpu/nova/guidelines.html#language