FROMLIST: mm: enable speculative fault handling through do_anonymous_page()

in x86 fault handler, only attempt spf if the vma is anonymous.

In do_handle_mm_fault(), let speculative page faults proceed as long
as they fall into anonymous vmas. This enables the speculative
handling code in __handle_mm_fault() and do_anonymous_page().

In handle_pte_fault(), if vmf->pte is set (the original pte was not
pte_none), catch speculative faults and return VM_FAULT_RETRY as
those cases are not implemented yet. Also assert that do_fault()
is not reached in the speculative case.

Signed-off-by: Michel Lespinasse <michel@lespinasse.org>
Link: https://lore.kernel.org/all/20220128131006.67712-20-michel@lespinasse.org/


Bug: 161210518
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I875106fcfa1084f570c2bf8f24a129bdce55316b