rust: gpuvm: add GpuVmCore::sm_map()

Finally also add the operation for creating new mappings. Mapping
operations need extra data in the context since they involve a vm_bo
coming from the outside.

Co-developed-by: Asahi Lina <lina+kernel@asahilina.net>
Signed-off-by: Asahi Lina <lina+kernel@asahilina.net>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260409-gpuvm-rust-v6-5-b16e6ada7261@google.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

2 files changed, 170 insertions, 6 deletions

diff --git a/rust/kernel/drm/gpuvm/mod.rs b/rust/kernel/drm/gpuvm/mod.rs
index a6436abd0f9c..dc755f248143 100644
--- a/rust/kernel/drm/gpuvm/mod.rs
+++ b/rust/kernel/drm/gpuvm/mod.rs
@@ -108,7 +108,7 @@ impl<T: DriverGpuVm> GpuVm<T> {
             vm_bo_alloc: GpuVmBo::<T>::ALLOC_FN,
             vm_bo_free: GpuVmBo::<T>::FREE_FN,
             vm_bo_validate: None,
-            sm_step_map: None,
+            sm_step_map: Some(Self::sm_step_map),
             sm_step_unmap: Some(Self::sm_step_unmap),
             sm_step_remap: Some(Self::sm_step_remap),
         }
@@ -266,6 +266,13 @@ pub trait DriverGpuVm: Sized + Send {
     /// The private data passed to callbacks.
     type SmContext<'ctx>;
 
+    /// Indicates that a new mapping should be created.
+    fn sm_step_map<'op, 'ctx>(
+        &mut self,
+        op: OpMap<'op, Self>,
+        context: &mut Self::SmContext<'ctx>,
+    ) -> Result<OpMapped<'op, Self>, Error>;
+
     /// Indicates that an existing mapping should be removed.
     fn sm_step_unmap<'op, 'ctx>(
         &mut self,
diff --git a/rust/kernel/drm/gpuvm/sm_ops.rs b/rust/kernel/drm/gpuvm/sm_ops.rs
index 05f81c638aef..69a8e5ab2821 100644
--- a/rust/kernel/drm/gpuvm/sm_ops.rs
+++ b/rust/kernel/drm/gpuvm/sm_ops.rs
@@ -8,6 +8,108 @@ struct SmData<'a, 'ctx, T: DriverGpuVm> {
     user_context: &'a mut T::SmContext<'ctx>,
 }
 
+/// Adds an extra field to `SmData` for `sm_map()` callbacks.
+///
+/// # Invariants
+///
+/// `self.vm_bo.gpuvm() == self.sm_data.gpuvm`.
+#[repr(C)]
+struct SmMapData<'a, 'ctx, T: DriverGpuVm> {
+    sm_data: SmData<'a, 'ctx, T>,
+    vm_bo: &'a GpuVmBo<T>,
+}
+
+/// The argument for [`UniqueRefGpuVm::sm_map`].
+pub struct OpMapRequest<'a, 'ctx, T: DriverGpuVm> {
+    /// Address in GPU virtual address space.
+    pub addr: u64,
+    /// Length of mapping to create.
+    pub range: u64,
+    /// Offset in GEM object.
+    pub gem_offset: u64,
+    /// The GEM object to map.
+    pub vm_bo: &'a GpuVmBo<T>,
+    /// The user-provided context type.
+    pub context: &'a mut T::SmContext<'ctx>,
+}
+
+impl<'a, 'ctx, T: DriverGpuVm> OpMapRequest<'a, 'ctx, T> {
+    fn raw_request(&self) -> bindings::drm_gpuvm_map_req {
+        bindings::drm_gpuvm_map_req {
+            map: bindings::drm_gpuva_op_map {
+                va: bindings::drm_gpuva_op_map__bindgen_ty_1 {
+                    addr: self.addr,
+                    range: self.range,
+                },
+                gem: bindings::drm_gpuva_op_map__bindgen_ty_2 {
+                    offset: self.gem_offset,
+                    obj: self.vm_bo.obj().as_raw(),
+                },
+            },
+        }
+    }
+}
+
+/// Represents an `sm_step_map` operation that has not yet been completed.
+pub struct OpMap<'op, T: DriverGpuVm> {
+    op: &'op bindings::drm_gpuva_op_map,
+    // Since these abstractions are designed for immediate mode, the VM BO needs to be
+    // pre-allocated, so we always have it available when we reach this point.
+    vm_bo: &'op GpuVmBo<T>,
+    // This ensures that 'op is invariant, so that `OpMap<'long, T>` does not
+    // coerce to `OpMap<'short, T>`. This ensures that the user can't return
+    // the wrong `OpMapped` value.
+    _invariant: PhantomData<*mut &'op mut T>,
+}
+
+impl<'op, T: DriverGpuVm> OpMap<'op, T> {
+    /// The base address of the new mapping.
+    pub fn addr(&self) -> u64 {
+        self.op.va.addr
+    }
+
+    /// The length of the new mapping.
+    pub fn length(&self) -> u64 {
+        self.op.va.range
+    }
+
+    /// The offset within the [`drm_gem_object`](DriverGpuVm::Object).
+    pub fn gem_offset(&self) -> u64 {
+        self.op.gem.offset
+    }
+
+    /// The [`drm_gem_object`](DriverGpuVm::Object) to map.
+    pub fn obj(&self) -> &T::Object {
+        // SAFETY: The `obj` pointer is guaranteed to be valid.
+        unsafe { <T::Object as IntoGEMObject>::from_raw(self.op.gem.obj) }
+    }
+
+    /// The [`GpuVmBo`] that the new VA will be associated with.
+    pub fn vm_bo(&self) -> &GpuVmBo<T> {
+        self.vm_bo
+    }
+
+    /// Use the pre-allocated VA to carry out this map operation.
+    pub fn insert(self, va: GpuVaAlloc<T>, va_data: impl PinInit<T::VaData>) -> OpMapped<'op, T> {
+        let va = va.prepare(va_data);
+        // SAFETY: By the type invariants we may access the interval tree.
+        unsafe { bindings::drm_gpuva_map(self.vm_bo.gpuvm().as_raw(), va, self.op) };
+
+        let _gpuva_guard = self.vm_bo().lock_gpuva();
+        // SAFETY: The va is prepared for insertion, and we hold the GEM lock.
+        unsafe { bindings::drm_gpuva_link(va, self.vm_bo.as_raw()) };
+
+        OpMapped {
+            _invariant: self._invariant,
+        }
+    }
+}
+
+/// Represents a completed [`OpMap`] operation.
+pub struct OpMapped<'op, T> {
+    _invariant: PhantomData<*mut &'op mut T>,
+}
+
 /// Represents an `sm_step_unmap` operation that has not yet been completed.
 pub struct OpUnmap<'op, T: DriverGpuVm> {
     op: &'op bindings::drm_gpuva_op_unmap,
@@ -213,6 +315,35 @@ pub struct OpRemapped<'op, T> {
 }
 
 impl<T: DriverGpuVm> UniqueRefGpuVm<T> {
+    /// Create a mapping, removing or remapping anything that overlaps.
+    ///
+    /// Internally calls the [`DriverGpuVm`] callbacks similar to [`Self::sm_unmap`], except that
+    /// the [`DriverGpuVm::sm_step_map`] is called once to create the requested mapping.
+    #[inline]
+    pub fn sm_map(&mut self, req: OpMapRequest<'_, '_, T>) -> Result {
+        if req.vm_bo.gpuvm() != &**self {
+            return Err(EINVAL);
+        }
+
+        let gpuvm = self.as_raw();
+        let raw_req = req.raw_request();
+        // INVARIANT: Checked above that `vm_bo.gpuvm() == self`.
+        let mut p = SmMapData {
+            sm_data: SmData {
+                gpuvm: self,
+                user_context: req.context,
+            },
+            vm_bo: req.vm_bo,
+        };
+        // SAFETY:
+        // * raw_request() creates a valid request.
+        // * The private data is valid to be interpreted as both SmData and SmMapData since the
+        //   first field of SmMapData is SmData.
+        to_result(unsafe {
+            bindings::drm_gpuvm_sm_map(gpuvm, (&raw mut p).cast(), &raw const raw_req)
+        })
+    }
+
     /// Remove any mappings in the given region.
     ///
     /// Internally calls [`DriverGpuVm::sm_step_unmap`] for ranges entirely contained within the
@@ -226,19 +357,45 @@ impl<T: DriverGpuVm> UniqueRefGpuVm<T> {
         };
         // SAFETY:
         // * raw_request() creates a valid request.
-        // * The private data is valid to be interpreted as SmData.
+        // * The private data is a valid SmData.
         to_result(unsafe { bindings::drm_gpuvm_sm_unmap(gpuvm, (&raw mut p).cast(), addr, length) })
     }
 }
 
 impl<T: DriverGpuVm> GpuVm<T> {
     /// # Safety
-    /// Must be called from `sm_unmap` with a pointer to `SmData`.
+    /// Must be called from `sm_map` with a pointer to `SmMapData`.
+    pub(super) unsafe extern "C" fn sm_step_map(
+        op: *mut bindings::drm_gpuva_op,
+        p: *mut c_void,
+    ) -> c_int {
+        // SAFETY: If we reach `sm_step_map` then we were called from `sm_map` which always passes
+        // an `SmMapData` as private data.
+        let p = unsafe { &mut *p.cast::<SmMapData<'_, '_, T>>() };
+        let op = OpMap {
+            // SAFETY: sm_step_map is called with a map operation.
+            op: unsafe { &(*op).__bindgen_anon_1.map },
+            vm_bo: p.vm_bo,
+            _invariant: PhantomData,
+        };
+        match p
+            .sm_data
+            .gpuvm
+            .data()
+            .sm_step_map(op, p.sm_data.user_context)
+        {
+            Ok(OpMapped { .. }) => 0,
+            Err(err) => err.to_errno(),
+        }
+    }
+
+    /// # Safety
+    /// Must be called from `sm_map` or `sm_unmap` with a pointer to `SmMapData` or `SmData`.
     pub(super) unsafe extern "C" fn sm_step_unmap(
         op: *mut bindings::drm_gpuva_op,
         p: *mut c_void,
     ) -> c_int {
-        // SAFETY: The caller provides a pointer to `SmData`.
+        // SAFETY: The caller provides a pointer that can be treated as `SmData`.
         let p = unsafe { &mut *p.cast::<SmData<'_, '_, T>>() };
         let op = OpUnmap {
             // SAFETY: sm_step_unmap is called with an unmap operation.
@@ -252,12 +409,12 @@ impl<T: DriverGpuVm> GpuVm<T> {
     }
 
     /// # Safety
-    /// Must be called from `sm_unmap` with a pointer to `SmData`.
+    /// Must be called from `sm_map` or `sm_unmap` with a pointer to `SmMapData` or `SmData`.
     pub(super) unsafe extern "C" fn sm_step_remap(
         op: *mut bindings::drm_gpuva_op,
         p: *mut c_void,
     ) -> c_int {
-        // SAFETY: The caller provides a pointer to `SmData`.
+        // SAFETY: The caller provides a pointer that can be treated as `SmData`.
         let p = unsafe { &mut *p.cast::<SmData<'_, '_, T>>() };
         let op = OpRemap {
             // SAFETY: sm_step_remap is called with a remap operation.