Re: [Crash-utility] [PATCH v2] x86_64: Make the conversion between 4level and 5level paging automatically

At 07/12/2018 02:23 AM, Dave Anderson wrote: > > > ----- Original Message ----- >> >> >> ----- Original Message ----- >>> Hi Dave, >>> >>> At 07/11/2018 03:33 AM, Dave Anderson wrote: >>>> >>>> The final phase of support would be making this work: >>>> >>>> static int >>>> x86_64_task_uses_5level(struct task_context *tc) >>>> { >>>> return FALSE; >>>> } >>>> >>>> Have you had a chance to look at how that can be done? >>>> >>> >>> I have no idea to check if 5level paging is used in User-space. >>> >>> You gave me some methods, and I have try: >>> >>> -The MAP_FIXED flag >>> -check if the contents of the page directory or p4d is 'flods' >> >> It would be most helpful if you can compare two tasks, one with 5-level >> and one without, and see if there's anything obviously different. >> (I don't know what "flods" means) > > Ah, sorry, you mean if the top-level page directory folds back into itself. > > So yes, I wonder if it would be obvious enough by checking whether the > top-level pgd folds back into itself, and if so, 4-levels of page tables > are in use? But if that were the case, it seems that the 5-level translation > code would work on both types of user-space tasks. I just don't understand > how it's supposed to work. > OK, let me try to clarify if the the 5-level translation code would work on both types of user-space tasks at first. ;-) Thank you so much for you kind explanation! dou.