linux-kernel - Re: [PATCH v2 3/7] mm: Add batched versions of ptep_modify_prot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <2b66e535-301b-4ab0-932f-46db376be410@lucifer.local>
Date: Tue, 6 May 2025 16:03:45 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Dev Jain <dev.jain@....com>, akpm@...ux-foundation.org,
        ryan.roberts@....com, willy@...radead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, catalin.marinas@....com, will@...nel.org,
        Liam.Howlett@...cle.com, vbabka@...e.cz, jannh@...gle.com,
        anshuman.khandual@....com, peterx@...hat.com, joey.gouly@....com,
        ioworker0@...il.com, baohua@...nel.org, kevin.brodsky@....com,
        quic_zhenhuah@...cinc.com, christophe.leroy@...roup.eu,
        yangyicong@...ilicon.com, linux-arm-kernel@...ts.infradead.org,
        namit@...are.com, hughd@...gle.com, yang@...amperecomputing.com,
        ziy@...dia.com
Subject: Re: [PATCH v2 3/7] mm: Add batched versions of
 ptep_modify_prot_start/commit

On Tue, May 06, 2025 at 04:30:18PM +0200, David Hildenbrand wrote:
> On 30.04.25 16:37, Lorenzo Stoakes wrote:
> > On Wed, Apr 30, 2025 at 11:55:12AM +0530, Dev Jain wrote:
> > >
> > >
> > > On 29/04/25 7:22 pm, Lorenzo Stoakes wrote:
> > > > On Tue, Apr 29, 2025 at 10:53:32AM +0530, Dev Jain wrote:
> > > > > Batch ptep_modify_prot_start/commit in preparation for optimizing mprotect.
> > > > > Architecture can override these helpers.
> > > > >
> > > > > Signed-off-by: Dev Jain <dev.jain@....com>
> > > > > ---
> > > > >    include/linux/pgtable.h | 38 ++++++++++++++++++++++++++++++++++++++
> > > > >    1 file changed, 38 insertions(+)
> > > > >
> > > > > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> > > > > index b50447ef1c92..ed287289335f 100644
> > > > > --- a/include/linux/pgtable.h
> > > > > +++ b/include/linux/pgtable.h
> > > > > @@ -891,6 +891,44 @@ static inline void wrprotect_ptes(struct mm_struct *mm, unsigned long addr,
> > > > >    }
> > > > >    #endif
> > > > >
> > > > > +/* See the comment for ptep_modify_prot_start */
> > > >
> > > > I feel like you really should add a little more here, perhaps point out
> > > > that it's batched etc.
> > >
> > > Sure. I couldn't easily figure out a way to write the documentation nicely,
> > > I'll do it this time.
> >
> > Thanks! Though see the discussion with Ryan also.
> >
> > >
> > > >
> > > > > +#ifndef modify_prot_start_ptes
> > > > > +static inline pte_t modify_prot_start_ptes(struct vm_area_struct *vma,
> > > > > +		unsigned long addr, pte_t *ptep, unsigned int nr)
> > > >
> > > > This name is a bit confusing, it's not any ptes, it's those pte entries
> > > > belonging to a large folio capped to the PTE table right that you are
> > > > batching right?
> > >
> > > yes, but I am just following the convention. See wrprotect_ptes(), etc. I
> > > don't have a strong preference anyways.
> > >
> > > >
> > > > Perhaps modify_prot_start_large_folio() ? Or something with 'batched' in
> > > > the name?
> > >
> > > How about modify_prot_start_batched_ptes()?
> >
> > I like this :) Ryan - that work for you, or do you feel _batched_ should be
> > dropped here?
>
>
> modify_prot_start_folio_ptes ?
>
> But I would rather go with
>
> modify_prot_folio_ptes_start
>
> The "batched" is implicit, and "large folio" is not required if it's more
> than one pte ...

Yeah that works for me! The mention of folio with plural does neatly imply
the rest.

Naming is hard :P

>
> :)
>
> --
> Cheers,
>
> David / dhildenb
>