Re: [RFC PATCH v2 9/9] mm: Introduce Copy-On-Write PTE table

[Chih-En Lin]

On Thu, Sep 29, 2022 at 06:40:36PM +0000, Nadav Amit wrote:
> On Sep 29, 2022, at 11:29 AM, Chih-En Lin <shiyn.lin@xxxxxxxxx> wrote:
> 
> > That case could be caught in copy_pte_range(): in case we'd have to allocate
> >> a page via page_copy_prealloc(), we'd have to fall back to the ordinary
> >> "separate page table for the child" way of doing things.
> >> 
> >> But that looks doable to me.
> > 
> > Sounds good. :)
> 
> Chih-En, I admit I did not fully read the entire correspondence and got deep
> into all the details.
> 
> I would note, however, that there are several additional components that I
> did not see (and perhaps missed) in your patches. Basically, there are many
> page-table manipulations that are done not through the page-fault handler or
> reclamation mechanisms. I did not see any of them being addressed.
> 
> So if/when you send a new version, please have a look at mprotect(),
> madvise(), soft-dirty, userfaultfd and THP. In these cases, I presume, you
> would have to COW-break (aka COW-unshare) the page-tables.
> 

Sure. Before I send the new version I will try to handle all of them.
Thank you for the note.

Thanks,
Chih-En Lin