Pulling slabs out of struct page

As I understand it, on Intel chips that support memory failure recovery, failed writes may not be notified at all. (I’ve at least been told this is true for the TDX style machine checks.)

And Linux’s entry code makes quite weak guarantees about recoverability of machine checks: we make a best (and pretty good) effort to recover from a fault in user code, and we try to recover from kernel code with exception table entries. If normal kernel code without an exception table entry hits a memory failure entry, forget about struct page: we may be 100% dead regardless because we have no idea how to resume execution.

If we hit a machine check with an exception handler, then we know the program counter, and we have a full register file. Figuring out the failed virtual address isn’t much of a problem even if the hardware doesn’t help.