Currently the DRM GPUVM offers common infrastructure to track GPU VA
allocations and mappings, generically connect GPU VA mappings to their
backing buffers and perform more complex mapping operations on the GPU VA
space.
However, there are more design patterns commonly used by drivers, which
can potentially be generalized in order to make the DRM GPUVM represent
a basis for GPU-VM implementations. In this context, this patch aims
at generalizing the following elements.
1) Provide a common dma-resv for GEM objects not being used outside of
this GPU-VM.
2) Provide tracking of external GEM objects (GEM objects which are
shared with other GPU-VMs).
3) Provide functions to efficiently lock all GEM objects dma-resv the
GPU-VM contains mappings of.
4) Provide tracking of evicted GEM objects the GPU-VM contains mappings
of, such that validation of evicted GEM objects is accelerated.
5) Provide some convinience functions for common patterns.
Big thanks to Boris Brezillon for his help to figure out locking for
drivers updating the GPU VA space within the fence signalling path.
Suggested-by: Matthew Brost <matthew.brost@xxxxxxxxx>
Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
---
drivers/gpu/drm/drm_gpuvm.c | 642 ++++++++++++++++++++++++++++++++++++
include/drm/drm_gpuvm.h | 240 ++++++++++++++
2 files changed, 882 insertions(+)
diff --git a/drivers/gpu/drm/drm_gpuvm.c b/drivers/gpu/drm/drm_gpuvm.c
index 27100423154b..770bb3d68d1f 100644
--- a/drivers/gpu/drm/drm_gpuvm.c
+++ b/drivers/gpu/drm/drm_gpuvm.c
@@ -82,6 +82,21 @@
* &drm_gem_object list of &drm_gpuvm_bos for an existing instance of this
* particular combination. If not existent a new instance is created and linked
* to the &drm_gem_object.
+ *
+ * &drm_gpuvm_bo structures, since unique for a given &drm_gpuvm, are also used
+ * as entry for the &drm_gpuvm's lists of external and evicted objects. Those
+ * list are maintained in order to accelerate locking of dma-resv locks and
+ * validation of evicted objects bound in a &drm_gpuvm. For instance, all
+ * &drm_gem_object's &dma_resv of a given &drm_gpuvm can be locked by calling
+ * drm_gpuvm_exec_lock(). Once locked drivers can call drm_gpuvm_validate() in
+ * order to validate all evicted &drm_gem_objects. It is also possible to lock
+ * additional &drm_gem_objects by providing the corresponding parameters to
+ * drm_gpuvm_exec_lock() as well as open code the &drm_exec loop while making
+ * use of helper functions such as drm_gpuvm_prepare_range() or
+ * drm_gpuvm_prepare_objects().
+ *
+ * Every bound &drm_gem_object is treated as external object when its &dma_resv
+ * structure is different than the &drm_gpuvm's common &dma_resv structure.
*/
/**
@@ -429,6 +444,20 @@
* Subsequent calls to drm_gpuvm_bo_obtain() for the same &drm_gpuvm and
* &drm_gem_object must be able to observe previous creations and destructions
* of &drm_gpuvm_bos in order to keep instances unique.
+ *
+ * The &drm_gpuvm's lists for keeping track of external and evicted objects are
+ * protected against concurrent insertion / removal and iteration internally.
+ *
+ * However, drivers still need ensure to protect concurrent calls to functions
+ * iterating those lists, namely drm_gpuvm_prepare_objects() and
+ * drm_gpuvm_validate().
+ *
+ * Alternatively, drivers can set the &DRM_GPUVM_RESV_PROTECTED flag to indicate
+ * that the corresponding &dma_resv locks are held in order to protect the
+ * lists. If &DRM_GPUVM_RESV_PROTECTED is set, internal locking is disabled and
+ * the corresponding lockdep checks are enabled. This is an optimization for
+ * drivers which are capable of taking the corresponding &dma_resv locks and
+ * hence do not require internal locking.
*/
/**
@@ -641,6 +670,195 @@
* }
*/
+/**
+ * get_next_vm_bo_from_list() - get the next vm_bo element
+ * @__gpuvm: The GPU VM
+ * @__list_name: The name of the list we're iterating on
+ * @__local_list: A pointer to the local list used to store already iterated items
+ * @__prev_vm_bo: The previous element we got from drm_gpuvm_get_next_cached_vm_bo()
+ *
+ * This helper is here to provide lockless list iteration. Lockless as in, the
+ * iterator releases the lock immediately after picking the first element from
+ * the list, so list insertion deletion can happen concurrently.
+ *
+ * Elements popped from the original list are kept in a local list, so removal
+ * and is_empty checks can still happen while we're iterating the list.
+ */
+#define get_next_vm_bo_from_list(__gpuvm, __list_name, __local_list, __prev_vm_bo) \
+ ({ \
+ struct drm_gpuvm_bo *__vm_bo = NULL; \
+ \
+ drm_gpuvm_bo_put(__prev_vm_bo); \
+ \
+ spin_lock(&(__gpuvm)->__list_name.lock); \
+ if (!(__gpuvm)->__list_name.local_list) \
+ (__gpuvm)->__list_name.local_list = __local_list; \
+ else \
+ WARN_ON((__gpuvm)->__list_name.local_list != __local_list); \
+ \
+ while (!list_empty(&(__gpuvm)->__list_name.list)) { \
+ __vm_bo = list_first_entry(&(__gpuvm)->__list_name.list, \
+ struct drm_gpuvm_bo, \
+ list.entry.__list_name); \
+ if (kref_get_unless_zero(&__vm_bo->kref)) { \
+ list_move_tail(&(__vm_bo)->list.entry.__list_name, \
+ __local_list); \
+ break; \
+ } else { \
+ list_del_init(&(__vm_bo)->list.entry.__list_name); \
+ __vm_bo = NULL; \
+ } \
+ } \
+ spin_unlock(&(__gpuvm)->__list_name.lock); \
+ \
+ __vm_bo; \
+ })
+
+/**
+ * for_each_vm_bo_in_list() - internal vm_bo list iterator
+ *
+ * This helper is here to provide lockless list iteration. Lockless as in, the
+ * iterator releases the lock immediately after picking the first element from the
+ * list, hence list insertion and deletion can happen concurrently.
+ *
+ * It is not allowed to re-assign the vm_bo pointer from inside this loop.
+ *
+ * Typical use:
+ *
+ * struct drm_gpuvm_bo *vm_bo;
+ * LIST_HEAD(my_local_list);
+ *
+ * ret = 0;
+ * for_each_vm_bo_in_list(gpuvm, <list_name>, &my_local_list, vm_bo) {
+ * ret = do_something_with_vm_bo(..., vm_bo);
+ * if (ret)
+ * break;
+ * }
+ * drm_gpuvm_bo_put(vm_bo);
+ * restore_vm_bo_list(gpuvm, <list_name>, &my_local_list);
+ *
+ *
+ * Only used for internal list iterations, not meant to be exposed to the outside
+ * world.
+ */
+#define for_each_vm_bo_in_list(__gpuvm, __list_name, __local_list, __vm_bo) \
+ for (__vm_bo = get_next_vm_bo_from_list(__gpuvm, __list_name, \
+ __local_list, NULL); \
+ __vm_bo; \
+ __vm_bo = get_next_vm_bo_from_list(__gpuvm, __list_name, \
+ __local_list, __vm_bo))
+
+static inline void
+__restore_vm_bo_list(struct drm_gpuvm *gpuvm, spinlock_t *lock,
+ struct list_head *list, struct list_head **local_list)
