Rust bindings for gem shmem + iosys_map

index a7f682e95c018..5c215e83c1b09 100644
@@ -15,6 +15,43 @@
 };
 use core::{ops::Deref, ptr::NonNull};
 
+/// A macro for implementing [`AlwaysRefCounted`] for any GEM object type.
+///
+/// Since all GEM objects use the same refcounting scheme.
+#[macro_export]
+macro_rules! impl_aref_for_gem_obj {
+    (
+        impl $( <$( $tparam_id:ident ),+> )? for $type:ty
+        $(
+            where
+                $( $bind_param:path : $bind_trait:path ),+
+        )?
+    ) => {
+        // SAFETY: All gem objects are refcounted
+        unsafe impl $( <$( $tparam_id ),+> )? $crate::types::AlwaysRefCounted for $type
+        where
+            Self: IntoGEMObject,
+            $( $( $bind_param : $bind_trait ),+ )?
+        {
+            fn inc_ref(&self) {
+                // SAFETY: The existence of a shared reference guarantees that the refcount is
+                // non-zero.
+                unsafe { bindings::drm_gem_object_get(self.as_raw()) };
+            }
+
+            unsafe fn dec_ref(obj: core::ptr::NonNull<Self>) {
+                // SAFETY: `obj` is a valid pointer to an `Object<T>`.
+                let obj = unsafe { obj.as_ref() }.as_raw();
+
+                // SAFETY: The safety requirements guarantee that the refcount is non-zero.
+                unsafe { bindings::drm_gem_object_put(obj) };
+            }
+        }
+    };
+}
+
+pub(crate) use impl_aref_for_gem_obj;
+
 /// A type alias for retrieving a [`Driver`]s [`DriverFile`] implementation from its
 /// [`DriverObject`] implementation.
 ///

@@ -252,21 +289,7 @@ extern "C" fn free_callback(obj: *mut bindings::drm_gem_object) {
     }
 }
 
-// SAFETY: Instances of `Object<T>` are always reference-counted.
-unsafe impl<T: DriverObject> crate::types::AlwaysRefCounted for Object<T> {
-    fn inc_ref(&self) {
-        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
-    }
-
-    unsafe fn dec_ref(obj: NonNull<Self>) {
-        // SAFETY: `obj` is a valid pointer to an `Object<T>`.
-        let obj = unsafe { obj.as_ref() };
-
-        // SAFETY: The safety requirements guarantee that the refcount is non-zero.
-        unsafe { bindings::drm_gem_object_put(obj.as_raw()) }
-    }
-}
+impl_aref_for_gem_obj!(impl<T> for Object<T> where T: DriverObject);
 
 impl<T: DriverObject> super::private::Sealed for Object<T> {}
 

index 2e43c66635a2c..07f79e125c329 100644
@@ -48,6 +48,7 @@
 #include <linux/cpumask.h>
 #include <linux/cred.h>
 #include <linux/debugfs.h>
+#include <linux/dma-resv.h>
 #include <linux/device/faux.h>
 #include <linux/dma-direction.h>
 #include <linux/dma-mapping.h>

new file mode 100644
index 0000000000000..05501cb814513
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/dma-resv.h>
+
+int rust_helper_dma_resv_lock(struct dma_resv *obj, struct ww_acquire_ctx *ctx)
+{
+	return dma_resv_lock(obj, ctx);
+}
+
+void rust_helper_dma_resv_unlock(struct dma_resv *obj)
+{
+	dma_resv_unlock(obj);
+}

index 551da6c9b5064..36d40f911345c 100644
@@ -25,6 +25,7 @@
 #include "cred.c"
 #include "device.c"
 #include "dma.c"
+#include "dma-resv.c"
 #include "drm.c"
 #include "err.c"
 #include "irq.c"

index 5c215e83c1b09..ec3c1b1775196 100644
@@ -199,6 +199,18 @@ fn create_mmap_offset(&self) -> Result<u64> {
 
 impl<T: IntoGEMObject> BaseObject for T {}
 
+/// Crate-private base operations shared by all GEM object classes.
+#[expect(unused)]
+pub(crate) trait BaseObjectPrivate: IntoGEMObject {
+    /// Return a pointer to this object's dma_resv.
+    fn raw_dma_resv(&self) -> *mut bindings::dma_resv {
+        // SAFETY: `as_gem_obj()` always returns a valid pointer to the base DRM gem object
+        unsafe { (*self.as_raw()).resv }
+    }
+}
+
+impl<T: IntoGEMObject> BaseObjectPrivate for T {}
+
 /// A base GEM object.
 ///
 /// # Invariants

index 2760ba4f3450b..173077eeb2def 100644
@@ -18,8 +18,9 @@ pub(crate) struct NovaObject {}
 
 impl gem::DriverObject for NovaObject {
     type Driver = NovaDriver;
+    type Args = ();
 
-    fn new(_dev: &NovaDevice, _size: usize) -> impl PinInit<Self, Error> {
+    fn new(_dev: &NovaDevice, _size: usize, _args: Self::Args) -> impl PinInit<Self, Error> {
         try_pin_init!(NovaObject {})
     }
 }

@@ -33,7 +34,7 @@ pub(crate) fn new(dev: &NovaDevice, size: usize) -> Result<ARef<gem::Object<Self
             return Err(EINVAL);
         }
 
-        gem::Object::new(dev, aligned_size)
+        gem::Object::new(dev, aligned_size, ())
     }
 
     /// Look up a GEM object handle for a `File` and return an `ObjectRef` for it.

index 1273bf89dbd5d..bb5e7871efa94 100644
@@ -11,8 +11,9 @@ pub(crate) struct TyrObject {}
 
 impl gem::DriverObject for TyrObject {
     type Driver = TyrDriver;
+    type Args = ();
 
-    fn new(_dev: &TyrDevice, _size: usize) -> impl PinInit<Self, Error> {
+    fn new(_dev: &TyrDevice, _size: usize, _args: ()) -> impl PinInit<Self, Error> {
         try_pin_init!(TyrObject {})
     }
 }

index ec3c1b1775196..4bcaee2d4b308 100644
@@ -64,8 +64,15 @@ pub trait DriverObject: Sync + Send + Sized {
     /// Parent `Driver` for this object.
     type Driver: drm::Driver;
 
+    /// The data type to use for passing arguments to [`DriverObject::new`].
+    type Args;
+
     /// Create a new driver data object for a GEM object of a given size.
-    fn new(dev: &drm::Device<Self::Driver>, size: usize) -> impl PinInit<Self, Error>;
+    fn new(
+        dev: &drm::Device<Self::Driver>,
+        size: usize,
+        args: Self::Args,
+    ) -> impl PinInit<Self, Error>;
 
     /// Open a new handle to an existing object, associated with a File.
     fn open(_obj: &<Self::Driver as drm::Driver>::Object, _file: &DriverFile<Self>) -> Result {

@@ -244,11 +251,11 @@ impl<T: DriverObject> Object<T> {
     };
 
     /// Create a new GEM object.
-    pub fn new(dev: &drm::Device<T::Driver>, size: usize) -> Result<ARef<Self>> {
+    pub fn new(dev: &drm::Device<T::Driver>, size: usize, args: T::Args) -> Result<ARef<Self>> {
         let obj: Pin<KBox<Self>> = KBox::pin_init(
             try_pin_init!(Self {
                 obj: Opaque::new(bindings::drm_gem_object::default()),
-                data <- T::new(dev, size),
+                data <- T::new(dev, size, args),
             }),
             GFP_KERNEL,
         )?;

index 07f79e125c329..ad644f3d62cc3 100644
@@ -33,6 +33,7 @@
 #include <drm/drm_drv.h>
 #include <drm/drm_file.h>
 #include <drm/drm_gem.h>
+#include <drm/drm_gem_shmem_helper.h>
 #include <drm/drm_ioctl.h>
 #include <kunit/test.h>
 #include <linux/auxiliary_bus.h>

@@ -60,6 +61,7 @@
 #include <linux/interrupt.h>
 #include <linux/fs.h>
 #include <linux/ioport.h>
+#include <linux/iosys-map.h>
 #include <linux/jiffies.h>
 #include <linux/jump_label.h>
 #include <linux/mdio.h>

57 lines not on this page · raw message

index 4bcaee2d4b308..c5af551f7e13e 100644
@@ -3,6 +3,8 @@
 //! DRM GEM API
 //!
 //! C header: [`include/drm/drm_gem.h`](srctree/include/drm/drm_gem.h)
+#[cfg(CONFIG_DRM_GEM_SHMEM_HELPER = "y")]
+pub mod shmem;
 
 use crate::{
     alloc::flags::*,

@@ -207,7 +209,6 @@ fn create_mmap_offset(&self) -> Result<u64> {
 impl<T: IntoGEMObject> BaseObject for T {}
 
 /// Crate-private base operations shared by all GEM object classes.
-#[expect(unused)]
 pub(crate) trait BaseObjectPrivate: IntoGEMObject {
     /// Return a pointer to this object's dma_resv.
     fn raw_dma_resv(&self) -> *mut bindings::dma_resv {

225 lines not on this page · raw message

index 45b95d60a3ec7..21ccb6c1824be 100644
@@ -173,6 +173,25 @@ pub fn sg_table(&self) -> Result<&scatterlist::SGTable> {
         // pointer to a scatterlist
         Ok(unsafe { scatterlist::SGTable::from_raw(sgt) })
     }
+
+    /// Creates (if necessary) and returns an owned reference to a scatter-gather table of DMA pages
+    /// for this object.
+    ///
+    /// This is the same as [`sg_table`](Self::sg_table), except that it instead returns an
+    /// [`shmem::SGTable`] which holds a reference to the associated gem object, instead of a
+    /// reference to an [`scatterlist::SGTable`].
+    ///
+    /// This will pin the object in memory.
+    ///
+    /// [`shmem::SGTable`]: SGTable
+    pub fn owned_sg_table(&self) -> Result<SGTable<T>> {
+        Ok(SGTable {
+            sgt: self.sg_table()?.into(),
+            // INVARIANT: We take an owned refcount to `self` here, ensuring that `sgt` remains
+            // valid for as long as this `SGTable`.
+            _owner: self.into(),
+        })
+    }
 }
 
 impl<T: DriverObject> Deref for Object<T> {

@@ -223,3 +242,34 @@ impl<T: DriverObject> driver::AllocImpl for Object<T> {
         dumb_map_offset: None,
     };
 }
+
+/// An owned reference to a scatter-gather table of DMA address spans for a GEM shmem object.
+///
+/// This object holds an owned reference to the underlying GEM shmem object, ensuring that the
+/// [`scatterlist::SGTable`] referenced by this type remains valid for the lifetime of this object.
+///
+/// # Invariants
+///
+/// - `sgt` is kept alive by `_owner`, ensuring it remains valid for as long as `Self`.
+/// - `sgt` corresponds to the owned object in `_owner`.
+/// - This object is only exposed in situations where we know the underlying `SGTable` will not be
+///   modified for the lifetime of this object. Thus, it is safe to send/access this type across
+///   threads.
+pub struct SGTable<T: DriverObject> {
+    sgt: NonNull<scatterlist::SGTable>,
+    _owner: ARef<Object<T>>,
+}
+
+// SAFETY: This object is thread-safe via our type invariants.
+unsafe impl<T: DriverObject> Send for SGTable<T> {}
+// SAFETY: This object is thread-safe via our type invariants.
+unsafe impl<T: DriverObject> Sync for SGTable<T> {}
+
+impl<T: DriverObject> Deref for SGTable<T> {
+    type Target = scatterlist::SGTable;
+
+    fn deref(&self) -> &Self::Target {
+        // SAFETY: Creating an immutable reference to this is safe via our type invariants.
+        unsafe { self.sgt.as_ref() }
+    }
+}

index 36d40f911345c..d549af697bd60 100644
@@ -31,6 +31,7 @@
 #include "irq.c"
 #include "fs.c"
 #include "io.c"
+#include "iosys_map.c"
 #include "jump_label.c"
 #include "kunit.c"
 #include "maple_tree.c"

new file mode 100644
index 0000000000000..b105261c3cf8a
@@ -0,0 +1,15 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/iosys-map.h>
+
+void rust_helper_iosys_map_memcpy_to(struct iosys_map *dst, size_t dst_offset,
+				     const void *src, size_t len)
+{
+	iosys_map_memcpy_to(dst, dst_offset, src, len);
+}
+
+void rust_helper_iosys_map_memcpy_from(void *dst, const struct iosys_map *src,
+				       size_t src_offset, size_t len)
+{
+	iosys_map_memcpy_from(dst, src, src_offset, len);
+}

614 lines not on this page · raw message

index 2581a356d1141..f727dbe2c8254 100644
@@ -101,6 +101,7 @@
 pub mod init;
 pub mod io;
 pub mod ioctl;
+pub mod iosys_map;
 pub mod iov;
 pub mod irq;
 pub mod jump_label;

index 21ccb6c1824be..62a2c12b9fe2a 100644
@@ -13,15 +13,18 @@
     container_of,
     drm::{device, driver, gem, private::Sealed},
     error::{from_err_ptr, to_result},
+    iosys_map::*,
     prelude::*,
     scatterlist,
+    transmute::*,
     types::{ARef, Opaque},
 };
 use core::{
+    mem::{self, MaybeUninit},
     ops::{Deref, DerefMut},
     ptr::NonNull,
 };
-use gem::{BaseObjectPrivate, DriverObject, IntoGEMObject};
+use gem::{BaseObject, BaseObjectPrivate, DriverObject, IntoGEMObject};
 
 /// A struct for controlling the creation of shmem-backed GEM objects.
 ///

@@ -192,6 +195,72 @@ pub fn owned_sg_table(&self) -> Result<SGTable<T>> {
             _owner: self.into(),
         })
     }
+
+    /// Attempt to create a [`RawIoSysMap`] from the gem object.
+    fn raw_vmap<U: AsBytes + FromBytes>(&self) -> Result<RawIoSysMap<U>> {
+        build_assert!(
+            mem::size_of::<U>() > 0,
+            "It doesn't make sense for the mapping type to be a ZST"
+        );
+
+        let mut map: MaybeUninit<bindings::iosys_map> = MaybeUninit::uninit();
+
+        // SAFETY: drm_gem_shmem_vmap can be called with the DMA reservation lock held
+        to_result(unsafe {
+            // TODO: see top of file
+            bindings::dma_resv_lock(self.raw_dma_resv(), core::ptr::null_mut());
+            let ret = bindings::drm_gem_shmem_vmap_locked(self.as_shmem(), map.as_mut_ptr());
+            bindings::dma_resv_unlock(self.raw_dma_resv());
+            ret
+        })?;
+
+        // SAFETY: if drm_gem_shmem_vmap did not fail, map is initialized now
+        Ok(unsafe { RawIoSysMap::from_raw(map.assume_init()) })
+    }
+
+    /// Unmap a [`RawIoSysMap`] from the gem object.
+    ///
+    /// # Safety
+    ///
+    /// - The caller promises that `map` came from a prior call to [`Self::raw_vmap`] on this gem
+    ///   object.
+    /// - The caller promises that the memory pointed to by `map` will no longer be accesed through
+    ///   this instance.
+    unsafe fn raw_vunmap<U: AsBytes + FromBytes>(&self, map: &mut RawIoSysMap<U>) {
+        let resv = self.raw_dma_resv();
+
+        // SAFETY:
+        // - This function is safe to call with the DMA reservation lock held
+        // - Our `ARef` is proof that the underlying gem object here is initialized and thus safe to
+        //   dereference.
+        unsafe {
+            // TODO: see top of file
+            bindings::dma_resv_lock(resv, core::ptr::null_mut());
+            bindings::drm_gem_shmem_vunmap_locked(self.as_shmem(), map.as_raw_mut());
+            bindings::dma_resv_unlock(resv);
+        }
+    }
+
+    /// Creates and returns a virtual kernel memory mapping for this object.
+    pub fn vmap<U: AsBytes + FromBytes>(&self) -> Result<VMapRef<'_, T, U>> {
+        let map = self.raw_vmap()?;
+
+        Ok(VMapRef {
+            // SAFETY:
+            // - The size of the vmap is the same as the size of the gem
+            // - The vmap will remain alive until this object is dropped.
+            map: unsafe { IoSysMapRef::new(map, self.size()) },
+            owner: self,
+        })
+    }
+
+    /// Creates and returns an owned reference to a virtual kernel memory mapping for this object.
+    pub fn owned_vmap<U: AsBytes + FromBytes>(&self) -> Result<VMap<T, U>> {
+        Ok(VMap {
+            map: self.raw_vmap()?,
+            owner: self.into(),
+        })
+    }
 }
 
 impl<T: DriverObject> Deref for Object<T> {

@@ -243,6 +312,95 @@ impl<T: DriverObject> driver::AllocImpl for Object<T> {
     };
 }
 
+/// A borrowed reference to a virtual mapping for a shmem-based GEM object in kernel address space.
+pub struct VMapRef<'a, D: DriverObject, T: AsBytes + FromBytes> {
+    map: IoSysMapRef<'a, T>,
+    owner: &'a Object<D>,
+}
+
+impl<'a, D: DriverObject, T: AsBytes + FromBytes> Clone for VMapRef<'a, D, T> {
+    fn clone(&self) -> Self {
+        // SAFETY: We have a successful vmap already, so this can't fail
+        unsafe { self.owner.vmap().unwrap_unchecked() }
+    }
+}
+
+impl<'a, D: DriverObject, T: AsBytes + FromBytes> Deref for VMapRef<'a, D, T> {
+    type Target = IoSysMapRef<'a, T>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.map
+    }
+}
+
+impl<'a, D: DriverObject, T: AsBytes + FromBytes> DerefMut for VMapRef<'a, D, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.map
+    }
+}
+
+impl<'a, D: DriverObject, T: AsBytes + FromBytes> Drop for VMapRef<'a, D, T> {
+    fn drop(&mut self) {
+        // SAFETY: Our existence is proof that this map was previously created using self.owner.
+        unsafe { self.owner.raw_vunmap(&mut self.map) };
+    }
+}
+
+/// An owned reference to a virtual mapping for a shmem-based GEM object in kernel address space.
+///
+/// # Invariants
+///
+/// - The memory pointed to by `map` is at least as large as `T`.
+/// - The memory pointed to by `map` remains valid at least until this object is dropped.
+pub struct VMap<D: DriverObject, T: AsBytes + FromBytes> {
+    map: RawIoSysMap<T>,
+    owner: ARef<Object<D>>,
+}
+
+impl<D: DriverObject, T: AsBytes + FromBytes> Clone for VMap<D, T> {
+    fn clone(&self) -> Self {
+        // SAFETY: We have a successful vmap already, so this can't fail
+        unsafe { self.owner.owned_vmap().unwrap_unchecked() }
+    }
+}
+
+impl<'a, D: DriverObject, T: AsBytes + FromBytes> From<VMapRef<'a, D, T>> for VMap<D, T> {
+    fn from(value: VMapRef<'a, D, T>) -> Self {
+        let this = Self {
+            map: value.map.clone(),
+            owner: value.owner.into(),
+        };
+
+        mem::forget(value);
+        this
+    }
+}
+
+impl<D: DriverObject, T: AsBytes + FromBytes> VMap<D, T> {
+    /// Return a reference to the iosys map for this `VMap`.
+    pub fn get(&self) -> IoSysMapRef<'_, T> {
+        // SAFETY: The size of the iosys_map is equivalent to the size of the gem object.
+        unsafe { IoSysMapRef::new(self.map.clone(), self.owner.size()) }
+    }
+
+    /// Borrows a reference to the object that owns this virtual mapping.
+    pub fn owner(&self) -> &Object<D> {
+        &self.owner
+    }
+}
+
+impl<D: DriverObject, T: AsBytes + FromBytes> Drop for VMap<D, T> {
+    fn drop(&mut self) {
+        // SAFETY: Our existence is proof that this map was previously created using self.owner
+        unsafe { self.owner.raw_vunmap(&mut self.map) };
+    }
+}
+
+/// SAFETY: `iosys_map` objects are safe to send across threads.
+unsafe impl<D: DriverObject, T: AsBytes + FromBytes> Send for VMap<D, T> {}
+/// SAFETY: `iosys_map` objects are safe to send across threads.
+unsafe impl<D: DriverObject, T: AsBytes + FromBytes> Sync for VMap<D, T> {}
+
 /// An owned reference to a scatter-gather table of DMA address spans for a GEM shmem object.
 ///
 /// This object holds an owned reference to the underlying GEM shmem object, ensuring that the

index 884a3d2be3348..fb1bb1bc03b73 100644
@@ -31,7 +31,7 @@
 
 impl<T: AsBytes + FromBytes> RawIoSysMap<T> {
     /// Convert from a raw `bindings::iosys_map`.
-    #[expect(unused)]
+    #[allow(unused)]
     #[inline]
     pub(crate) fn from_raw(val: bindings::iosys_map) -> Self {
         Self(val, PhantomData)