rust: drm: gpuvm: add SmContext lifetime bound

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>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260610-gpuvm_smcontext_lifetime_bound_v1-v1-1-531e7d2ee7b4@collabora.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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>(

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.