Re: [PATCH] rust: drm: gpuvm: add SmContext lifetime bound

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Jun 10, 2026 at 05:04:31PM -0700, Deborah Brouwer wrote:
> From: Boris Brezillon <boris.brezillon@collabora.com>
> 
> If a DriverGpuVm implementation is lifetime-parameterized, its
> SmContext<'ctx> type may depend on lifetimes carried by that driver
> implementation. In this case, SmContext<'ctx> is only valid if the
> driver implementation outlives 'ctx.
> 
> Add a Self: 'ctx bound to DriverGpuVm::SmContext<'ctx> to express that
> requirement. Then propagate the corresponding T: 'ctx bound to the GPUVM
> state machine helper types that store T::SmContext<'ctx>.
> 
> This allows drivers to provide lifetime-parameterized implementations of
> DriverGpuVm.
> 
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Deborah Brouwer <deborah.brouwer@collabora.com>
> ---
>  rust/kernel/drm/gpuvm/mod.rs    | 4 +++-
>  rust/kernel/drm/gpuvm/sm_ops.rs | 4 ++--
>  2 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/rust/kernel/drm/gpuvm/mod.rs b/rust/kernel/drm/gpuvm/mod.rs
> index ae58f6f667c1..1ec649fa50ea 100644
> --- a/rust/kernel/drm/gpuvm/mod.rs
> +++ b/rust/kernel/drm/gpuvm/mod.rs
> @@ -264,7 +264,9 @@ pub trait DriverGpuVm: Sized + Send {
>      type VmBoData;
>  
>      /// The private data passed to callbacks.
> -    type SmContext<'ctx>;
> +    type SmContext<'ctx>
> +    where
> +        Self: 'ctx;

This imposes the requirement that the GpuVm private data cannot contain
any references that expire during 'ctx. Since 'ctx represents the
duration of a call to sm_map() or sm_unmap(), this seems reasonable.

Reviewed-by: Alice Ryhl <aliceryhl@google.com>