[PATCH 4/4] drm/amdgpu: rework reserved VMID handling

[Christian König]

Instead of reserving a VMID for a single process allow that many
processes use the reserved ID. This allows for proper isolation
between the processes.

Signed-off-by: Christian König <christian.koenig at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c | 45 ++++++++++++-------------
 drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h |  3 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h  |  6 +---
 3 files changed, 24 insertions(+), 30 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
index 7e5aad241295..6481b43ffe25 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
@@ -279,12 +279,13 @@ static int amdgpu_vmid_grab_reserved(struct amdgpu_vm *vm,
 {
 	struct amdgpu_device *adev = ring->adev;
 	unsigned vmhub = ring->funcs->vmhub;
+	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
 	uint64_t fence_context = adev->fence_context + ring->idx;
 	bool needs_flush = vm->use_cpu_for_update;
 	uint64_t updates = amdgpu_vm_tlb_seq(vm);
 	int r;
 
-	*id = vm->reserved_vmid[vmhub];
+	*id = id_mgr->reserved;
 	if ((*id)->owner != vm->immediate.fence_context ||
 	    !amdgpu_vmid_compatible(*id, job) ||
 	    (*id)->flushed_updates < updates ||
@@ -464,31 +465,27 @@ int amdgpu_vmid_alloc_reserved(struct amdgpu_device *adev,
 			       struct amdgpu_vm *vm,
 			       unsigned vmhub)
 {
-	struct amdgpu_vmid_mgr *id_mgr;
-	struct amdgpu_vmid *idle;
-	int r = 0;
+	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
 
-	id_mgr = &adev->vm_manager.id_mgr[vmhub];
 	mutex_lock(&id_mgr->lock);
 	if (vm->reserved_vmid[vmhub])
 		goto unlock;
-	if (atomic_inc_return(&id_mgr->reserved_vmid_num) >
-	    AMDGPU_VM_MAX_RESERVED_VMID) {
-		DRM_ERROR("Over limitation of reserved vmid\n");
-		atomic_dec(&id_mgr->reserved_vmid_num);
-		r = -EINVAL;
-		goto unlock;
+
+	++id_mgr->reserved_use_count;
+	if (!id_mgr->reserved) {
+		struct amdgpu_vmid *id;
+
+		id = list_first_entry(&id_mgr->ids_lru, struct amdgpu_vmid,
+				      list);
+		/* Remove from normal round robin handling */
+		list_del_init(&id->list);
+		id_mgr->reserved = id;
 	}
-	/* Select the first entry VMID */
-	idle = list_first_entry(&id_mgr->ids_lru, struct amdgpu_vmid, list);
-	list_del_init(&idle->list);
-	vm->reserved_vmid[vmhub] = idle;
-	mutex_unlock(&id_mgr->lock);
+	vm->reserved_vmid[vmhub] = true;
 
-	return 0;
 unlock:
 	mutex_unlock(&id_mgr->lock);
-	return r;
+	return 0;
 }
 
 void amdgpu_vmid_free_reserved(struct amdgpu_device *adev,
@@ -498,12 +495,12 @@ void amdgpu_vmid_free_reserved(struct amdgpu_device *adev,
 	struct amdgpu_vmid_mgr *id_mgr = &adev->vm_manager.id_mgr[vmhub];
 
 	mutex_lock(&id_mgr->lock);
-	if (vm->reserved_vmid[vmhub]) {
-		list_add(&vm->reserved_vmid[vmhub]->list,
-			&id_mgr->ids_lru);
-		vm->reserved_vmid[vmhub] = NULL;
-		atomic_dec(&id_mgr->reserved_vmid_num);
+	if (vm->reserved_vmid[vmhub] &&
+	    !--id_mgr->reserved_use_count) {
+		/* give the reserved ID back to normal round robin */
+		list_add(&id_mgr->reserved->list, &id_mgr->ids_lru);
 	}
+	vm->reserved_vmid[vmhub] = false;
 	mutex_unlock(&id_mgr->lock);
 }
 
@@ -570,7 +567,7 @@ void amdgpu_vmid_mgr_init(struct amdgpu_device *adev)
 
 		mutex_init(&id_mgr->lock);
 		INIT_LIST_HEAD(&id_mgr->ids_lru);
-		atomic_set(&id_mgr->reserved_vmid_num, 0);
+		id_mgr->reserved_use_count = 0;
 
 		/* manage only VMIDs not used by KFD */
 		id_mgr->num_ids = adev->vm_manager.first_kfd_vmid;
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h
index 06c8a0034fa5..c573a8ffff47 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.h
@@ -67,7 +67,8 @@ struct amdgpu_vmid_mgr {
 	unsigned		num_ids;
 	struct list_head	ids_lru;
 	struct amdgpu_vmid	ids[AMDGPU_NUM_VMID];
-	atomic_t		reserved_vmid_num;
+	struct amdgpu_vmid	*reserved;
+	unsigned int		reserved_use_count;
 };
 
 int amdgpu_pasid_alloc(unsigned int bits);
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 6546e786bf00..094bb4807303 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -119,9 +119,6 @@ struct amdgpu_bo_vm;
 /* Reserve 2MB at top/bottom of address space for kernel use */
 #define AMDGPU_VA_RESERVED_SIZE			(2ULL << 20)
 
-/* max vmids dedicated for process */
-#define AMDGPU_VM_MAX_RESERVED_VMID	1
-
 /* See vm_update_mode */
 #define AMDGPU_VM_USE_CPU_FOR_GFX (1 << 0)
 #define AMDGPU_VM_USE_CPU_FOR_COMPUTE (1 << 1)
@@ -298,8 +295,7 @@ struct amdgpu_vm {
 	struct dma_fence	*last_unlocked;
 
 	unsigned int		pasid;
-	/* dedicated to vm */
-	struct amdgpu_vmid	*reserved_vmid[AMDGPU_MAX_VMHUBS];
+	bool			reserved_vmid[AMDGPU_MAX_VMHUBS];
 
 	/* Flag to indicate if VM tables are updated by CPU or GPU (SDMA) */
 	bool					use_cpu_for_update;
-- 
2.34.1