drm/amdkfd: Use atomic64_t type for pdd->tlb_seq

To support multi-thread update page table.
Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdkfd/kfd_priv.h

@@ -705,7 +705,7 @@ struct kfd_process_device {
 	/* VM context for GPUVM allocations */
 	struct file *drm_file;
 	void *drm_priv;
-	uint64_t tlb_seq;
+	atomic64_t tlb_seq;
 
 	/* GPUVM allocations storage */
 	struct idr alloc_idr;

drivers/gpu/drm/amd/amdkfd/kfd_process.c

@@ -1560,7 +1560,7 @@ int kfd_process_device_init_vm(struct kfd_process_device *pdd,
 		return ret;
 	}
 	pdd->drm_priv = drm_file->private_data;
-	pdd->tlb_seq = 0;
+	atomic64_set(&pdd->tlb_seq, 0);
 
 	ret = kfd_process_device_reserve_ib_mem(pdd);
 	if (ret)
@@ -1954,10 +1954,14 @@ void kfd_flush_tlb(struct kfd_process_device *pdd, enum TLB_FLUSH_TYPE type)
 	uint64_t tlb_seq = amdgpu_vm_tlb_seq(vm);
 	struct kfd_dev *dev = pdd->dev;
 
-	if (pdd->tlb_seq == tlb_seq)
+	/*
+	 * It can be that we race and lose here, but that is extremely unlikely
+	 * and the worst thing which could happen is that we flush the changes
+	 * into the TLB once more which is harmless.
+	 */
+	if (atomic64_xchg(&pdd->tlb_seq, tlb_seq) == tlb_seq)
 		return;
 
-	pdd->tlb_seq = tlb_seq;
 	if (dev->dqm->sched_policy == KFD_SCHED_POLICY_NO_HWS) {
 		/* Nothing to flush until a VMID is assigned, which
 		 * only happens when the first queue is created.