Change logic for translating a memory addresses, extra checks for invalid physical addresses.
Change logic for translating a memory addresses, extra checks for invalid
physical addresses.

andrewfu0325/gem5-aladdin,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,andrewfu0325/gem5-aladdin,haowu4682/gem5,haowu4682/gem5,haowu4682/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,haowu4682/gem5,LingxiaoJIA/gem5,haowu4682/gem5,LingxiaoJIA/gem5,LingxiaoJIA/gem5,haowu4682/gem5,LingxiaoJIA/gem5,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin