libhsakmt: Fix use of uninitialized variable

When is hsaKmtCreateQueue called first time for node
doorbells[NodeId].size is initialized to zero in init_process_doorbells
but used to calculate the doorbell offset. It works just by accident
because doorbells[NodeId].size is uint32_t so -1 will be 0xFFFFFFFF which
is zero extended into 0x00000000FFFFFFFF and it will work as long as mmap
offset bits are not within lower 32 bits.

Bug: https://github.com/RadeonOpenCompute/ROCT-Thunk-Interface/issues/78
Signed-off-by: Felix Kuehling <Felix.Kuehling@amd.com>
Change-Id: Ia791adfc51363d4704cb50fa4f01137b7dd48a75

src/queues.c

@@ -654,16 +654,16 @@ HSAKMT_STATUS HSAKMTAPI hsaKmtCreateQueue(HSAuint32 NodeId,
 	q->queue_id = args.queue_id;
 
 	if (IS_SOC15(q->gfxv)) {
+		HSAuint64 mask = DOORBELLS_PAGE_SIZE(DOORBELL_SIZE(q->gfxv)) - 1;
+
 		/* On SOC15 chips, the doorbell offset within the
 		 * doorbell page is included in the doorbell offset
 		 * returned by KFD. This allows CP queue doorbells to be
 		 * allocated dynamically (while SDMA queue doorbells fixed)
 		 * rather than based on the its process queue ID.
 		 */
-		doorbell_mmap_offset = args.doorbell_offset &
-			~(HSAuint64)(doorbells[NodeId].size - 1);
-		doorbell_offset = args.doorbell_offset &
-			(doorbells[NodeId].size - 1);
+		doorbell_mmap_offset = args.doorbell_offset & ~mask;
+		doorbell_offset = args.doorbell_offset & mask;
 	} else {
 		/* On older chips, the doorbell offset within the
 		 * doorbell page is based on the queue ID.