drm/amdgpu: Convert amdgpu userqueue management from IDR to XArray

This commit refactors the AMDGPU userqueue management subsystem to replace
IDR (ID Allocation) with XArray for improved performance, scalability, and
maintainability. The changes address several issues with the previous IDR
implementation and provide better locking semantics.

Key changes:

1. **Global XArray Introduction**:
   - Added `userq_doorbell_xa` to `struct amdgpu_device` for global queue tracking
   - Uses doorbell_index as key for efficient global lookup
   - Replaces the previous `userq_mgr_list` linked list approach

2. **Per-process XArray Conversion**:
   - Replaced `userq_idr` with `userq_mgr_xa` in `struct amdgpu_userq_mgr`
   - Maintains per-process queue tracking with queue_id as key
   - Uses XA_FLAGS_ALLOC for automatic ID allocation

3. **Locking Improvements**:
   - Removed global `userq_mutex` from `struct amdgpu_device`
   - Replaced with fine-grained XArray locking using XArray's internal spinlocks

4. **Runtime Idle Check Optimization**:
   - Updated `amdgpu_runtime_idle_check_userq()` to use xa_empty

5. **Queue Management Functions**:
   - Converted all IDR operations to equivalent XArray functions:
     - `idr_alloc()` → `xa_alloc()`
     - `idr_find()` → `xa_load()`
     - `idr_remove()` → `xa_erase()`
     - `idr_for_each()` → `xa_for_each()`

Benefits:
- **Performance**: XArray provides better scalability for large numbers of queues
- **Memory Efficiency**: Reduced memory overhead compared to IDR
- **Thread Safety**: Improved locking semantics with XArray's internal spinlocks

v2: rename userq_global_xa/userq_xa to userq_doorbell_xa/userq_mgr_xa
    Remove xa_lock and use its own lock.

v3: Set queue->userq_mgr = uq_mgr in amdgpu_userq_create()
v4: use xa_store_irq (Christian)
    hold the read side of the reset lock while creating/destroying queues and the manager data structure. (Chritian)

Acked-by: Alex Deucher <alexander.deucher@amd.com>
Suggested-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
index 036d8dd585cd..09da0617bfa2 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_userq.h
@@ -96,11 +96,15 @@ struct amdgpu_userq_funcs {
 
 /* Usermode queues for gfx */
 struct amdgpu_userq_mgr {
-	struct idr			userq_idr;
+	/**
+	 * @userq_mgr_xa: Per-process user queue map (queue ID → queue)
+	 * Key: queue_id (unique ID within the process's userq manager)
+	 * Value: struct amdgpu_usermode_queue
+	 */
+	struct xarray			userq_mgr_xa;
 	struct mutex			userq_mutex;
 	struct amdgpu_device		*adev;
 	struct delayed_work		resume_work;
-	struct list_head		list;
 	struct drm_file			*file;
 };