How to implement strictly-inclusive cache/ back invalidation?

[yongjiehuang]

Hi,
I want to try this method to implement a private L2 cache is strictly-inclusive of L1cache. I got a hint "send a snoop to fetch (if dirty) and invalidate the line above before evict a line in L2", which is the direction that I want to try.
Can somebody please give me more pointer on how to implement this? Like, any references can be found in isCachedAbove()?
And I also found a relevant question in https://www.mail-archive.com/gem5-users@gem5.org/msg19661.html but no one answers.
Best,
Yongjie