On Mon, Apr 19, 2021 at 07:03:01PM -0700, Jue Wang wrote: > On Tue, 13 Apr 2021 07:43:20 +0900, Naoya Horiguchi wrote: > > > This patch suggests to do page table walk to find the error virtual > > address. If we find multiple virtual addresses in walking, we now can't > > determine which one is correct, so we fall back to sending SIGBUS in > > kill_me_maybe() without error info as we do now. This corner case needs > > to be solved in the future. > > Instead of walking the page tables, I wonder what about the following idea: > > When failing to get vaddr, memory_failure just ensures the mapping is removed > and an hwpoisoned swap pte is put in place; or the original page is flagged with > PG_HWPOISONED and kept in the radix tree (e.g., for SHMEM THP). To remove the mapping, you need to know the virtual address :-) Well, I did try a patch that removed *all* user mappings (switched CR3 to swapper_pgdir) and returned to user. Then have the resulting page fault report the address. But that didn't work very well. > NOTE: no SIGBUS is sent to user space. > > Then do_machine_check just returns to user space to resume execution, the > re-execution will result in a #PF and should land to the exact page fault > handling code that generates a SIGBUS with the precise vaddr info: That's how SRAO (and other races) are supposed to work. -Tony
