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

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

[Deborah Brouwer]

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;
 
     /// Indicates that a new mapping should be created.
     fn sm_step_map<'op, 'ctx>(
diff --git a/rust/kernel/drm/gpuvm/sm_ops.rs b/rust/kernel/drm/gpuvm/sm_ops.rs
index 69a8e5ab2821..742c151b2540 100644
--- a/rust/kernel/drm/gpuvm/sm_ops.rs
+++ b/rust/kernel/drm/gpuvm/sm_ops.rs
@@ -3,7 +3,7 @@
 use super::*;
 
 /// The actual data that gets threaded through the callbacks.
-struct SmData<'a, 'ctx, T: DriverGpuVm> {
+struct SmData<'a, 'ctx, T: DriverGpuVm + 'ctx> {
     gpuvm: &'a mut UniqueRefGpuVm<T>,
     user_context: &'a mut T::SmContext<'ctx>,
 }
@@ -20,7 +20,7 @@ struct SmMapData<'a, 'ctx, T: DriverGpuVm> {
 }
 
 /// The argument for [`UniqueRefGpuVm::sm_map`].
-pub struct OpMapRequest<'a, 'ctx, T: DriverGpuVm> {
+pub struct OpMapRequest<'a, 'ctx, T: DriverGpuVm + 'ctx> {
     /// Address in GPU virtual address space.
     pub addr: u64,
     /// Length of mapping to create.

---
base-commit: 550dc7536644db2d67c6f8cf525bba682fba08d9
change-id: 20260610-gpuvm_smcontext_lifetime_bound_v1-f829c05d80c9

Best regards,
-- 
Deborah Brouwer <deborah.brouwer@collabora.com>

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

[Alice Ryhl]

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>