Re: [PATCH v2 2/2] x86/mm: implement free pmd/pte page interfaces

[Kani, Toshi]

On Sat, 2018-04-28 at 11:02 +0200, joro@xxxxxxxxxx wrote:
> On Fri, Apr 27, 2018 at 02:31:51PM +0000, Kani, Toshi wrote:
> > So, we can add the step 2 on top of this patch.
> >  1. Clear pud/pmd entry.
> >  2. System wide TLB flush <-- TO BE ADDED BY NEW PATCH
> >  3. Free its underlining pmd/pte page.
> 
> This still lacks the page-table synchronization and will thus not fix
> the BUG_ON being triggered.

The BUG_ON issue is specific to PAE that it syncs at the pmd level.
x86/64 does not have this issue since it syncs at the pgd or p4d level.

> > We do not need to revert this patch.  We can make the above change I
> > mentioned.
> 
> Please note that we are not in the merge window anymore and that any fix
> needs to be simple and obviously correct.

Understood.  Changing the x86/32 sync point is risky.  So, I am going to
revert the free page handling for PAE.   

Thanks,
-Toshi