Hi! See eXclusive Page Frame Ownership (https://lwn.net/Articles/700606/) which was posted way back in in 2016..
In the last couple of months there has been a slew of CPU issues that have complicated a lot of things. The latest - L1TF - is still fresh in folks's mind and it is especially acute to virtualization workloads. As such a bunch of various folks from different cloud companies (CCed) are looking at a way to make Linux kernel be more resistant to hardware having these sort of bugs. In particular we are looking at a way to "remove as many mappings from the global kernel address space as possible. Specifically, while being in the context of process A, memory of process B should not be visible in the kernel." (email from Julian Stecklina). That is the high-level view and how this could get done, well, that is why posting this on LKML/linux-hardening/kvm-devel/linux-mm to start the discussion. Usually I would start with a draft of RFC patches so folks can rip it apart, but thanks to other people (Juerg thank you!) it already exists: (see https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1222756.html) The idea would be to extend this to: 1) Only do it for processes that run under CPUS which are in isolcpus list. 2) Expand this to be a per-cpu page tables. That is each CPU has its own unique set of pagetables - naturally _START_KERNEL -> __end would be mapped but the rest would not. Thoughts? Is this possible? Crazy? Better ideas?
