linux-kernel - Re: [PATCH v5 09/16] kexec: enable KHO support for memory preservation

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 for Android: free password hash cracker in your pocket

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

Message-ID: <Z-Pt9yLP0cMR23cJ@kernel.org>
Date: Wed, 26 Mar 2025 08:07:19 -0400
From: Mike Rapoport <rppt@...nel.org>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Changyuan Lyu <changyuanl@...gle.com>, linux-kernel@...r.kernel.org,
	graf@...zon.com, akpm@...ux-foundation.org, luto@...nel.org,
	anthony.yznaga@...cle.com, arnd@...db.de, ashish.kalra@....com,
	benh@...nel.crashing.org, bp@...en8.de, catalin.marinas@....com,
	dave.hansen@...ux.intel.com, dwmw2@...radead.org,
	ebiederm@...ssion.com, mingo@...hat.com, jgowans@...zon.com,
	corbet@....net, krzk@...nel.org, mark.rutland@....com,
	pbonzini@...hat.com, pasha.tatashin@...een.com, hpa@...or.com,
	peterz@...radead.org, ptyadav@...zon.de, robh+dt@...nel.org,
	robh@...nel.org, saravanak@...gle.com,
	skinsburskii@...ux.microsoft.com, rostedt@...dmis.org,
	tglx@...utronix.de, thomas.lendacky@....com,
	usama.arif@...edance.com, will@...nel.org,
	devicetree@...r.kernel.org, kexec@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH v5 09/16] kexec: enable KHO support for memory
 preservation

On Mon, Mar 24, 2025 at 05:07:36PM -0300, Jason Gunthorpe wrote:
> On Mon, Mar 24, 2025 at 02:18:34PM -0400, Mike Rapoport wrote:
> > On Sun, Mar 23, 2025 at 03:55:52PM -0300, Jason Gunthorpe wrote:
> > > On Sat, Mar 22, 2025 at 03:12:26PM -0400, Mike Rapoport wrote:
> > >  
> > > > > > +		page->private = order;
> > > > > 
> > > > > Can't just set the page order directly? Why use private?
> > > > 
> > > > Setting the order means recreating the folio the way prep_compound_page()
> > > > does. I think it's better to postpone it until the folio is requested. This
> > > > way it might run after SMP is enabled. 
> > > 
> > > I see, that makes sense, but also it could stil use page->order..
> > 
> > But there's no page->order :)
> 
> I mean this:
> 
> static inline unsigned int folio_order(const struct folio *folio)
> {
>         if (!folio_test_large(folio))
>                 return 0;
>         return folio->_flags_1 & 0xff;
> }

I don't think it's better than page->private, KHO will need to
prep_compound_page() anyway so these will be overwritten there.
And I don't remember, but having those set before prep_compound_page()
might trigger VM_BUG_ON_PGFLAGS().
  
> Jason

-- 
Sincerely yours,
Mike.