drm/amdgpu: add limitation for dedicated vm number v4

Limit reserved vmids to 1 to avoid taking too many
out of commission and starving the system.

v2: move #define to amdgpu_vm.h
v3: move reserved vmid counter to id_manager,
and increase counter before allocating vmid
v4: rename to reserved_vmid_num

Signed-off-by: Chunming Zhou <David1.Zhou@amd.com>
Reviewed-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

2 files changed, 12 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
index 86ef0cdfd04d..2ea91392290c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c
@@ -551,6 +551,7 @@ static void amdgpu_vm_free_reserved_vmid(struct amdgpu_device *adev,
                 list_add(&vm->reserved_vmid[vmhub]->list,
                         &id_mgr->ids_lru);
                 vm->reserved_vmid[vmhub] = NULL;
+                atomic_dec(&id_mgr->reserved_vmid_num);
         }
         mutex_unlock(&id_mgr->lock);
 }
@@ -567,6 +568,13 @@ static int amdgpu_vm_alloc_reserved_vmid(struct amdgpu_device *adev,
         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;
+        }
         /* Select the first entry VMID */
         idle = list_first_entry(&id_mgr->ids_lru, struct amdgpu_vm_id, list);
         list_del_init(&idle->list);
@@ -2321,6 +2329,7 @@ void amdgpu_vm_manager_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);
 
                 /* skip over VMID 0, since it is the system VM */
                 for (j = 1; j < id_mgr->num_ids; ++j) {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
index 24ccf677f5a5..fb25bb747730 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.h
@@ -84,6 +84,8 @@ struct amdgpu_bo_list_entry;
 
 /* hardcode that limit for now */
 #define AMDGPU_VA_RESERVED_SIZE                 (8 << 20)
+/* max vmids dedicated for process */
+#define AMDGPU_VM_MAX_RESERVED_VMID     1
 
 struct amdgpu_vm_pt {
         struct amdgpu_bo        *bo;
@@ -154,6 +156,7 @@ struct amdgpu_vm_id_manager {
         unsigned                num_ids;
         struct list_head        ids_lru;
         struct amdgpu_vm_id     ids[AMDGPU_NUM_VM];
+        atomic_t                reserved_vmid_num;
 };
 
 struct amdgpu_vm_manager {