linux-kernel - Re: [PATCH v5 11/16] kexec: add config option for KHO

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

Message-ID: <CALu+AoS9=KttzqgR+xi11jur5eX7dBwUfOoueHoOss3eFn+Hkw@mail.gmail.com>
Date: Wed, 26 Mar 2025 20:09:55 +0800
From: Dave Young <dyoung@...hat.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: Baoquan He <bhe@...hat.com>, 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 11/16] kexec: add config option for KHO

On Wed, 26 Mar 2025 at 19:34, Mike Rapoport <rppt@...nel.org> wrote:
>
> Hi Dave,
>
> On Wed, Mar 26, 2025 at 05:17:16PM +0800, Dave Young wrote:
> > On Tue, 25 Mar 2025 at 16:36, Dave Young <dyoung@...hat.com> wrote:
> > >
> > > > >
> > > > > Have you tested kdump?  In my mind there are two issues,  one is with
> > > > > CMA enabled, it could cause kdump crashkernel memory reservation
> > > > > failures more often due to the fragmented low memory.  Secondly,  in
> > > >
> > > > kho scracth memorys are reserved much later than crashkernel, we may not
> > > > need to worry about it.
> > > > ====================
> > > > start_kernel()
> > > >   ......
> > > >   -->setup_arch(&command_line);
> > > >      -->arch_reserve_crashkernel();
> > > >   ......
> > > >   -->mm_core_init();
> > > >      -->kho_memory_init();
> > > >
> > > > > kdump kernel dump the crazy scratch memory in vmcore is not very
> > > > > meaningful.  Otherwise I suspect this is not tested under kdump.  If
> > > > > so please disable this option for kdump.
> > >
> > > Ok,  it is fine if this is the case, thanks Baoquan for clearing this worry.
> > >
> > > But the other concerns are still need to address, eg. KHO use cases
> > > are not good for kdump.
> > > There could be more to think about.
> > > eg. the issues talked in thread:
> > > https://lore.kernel.org/lkml/Z7dc9Cd8KX3b_brB@dwarf.suse.cz/T/
> >
> > Rethink about this,  other than previous concerns.  Transferring the
> > old kernel state to kdump kernel makes no sense since the old state is
> > not stable as the kernel has crashed.
>
> KHO won't be active for kdump case. The KHO segments are only added to
> kexec_image and never to kexec_crash_image.

Good to know, thanks!

>
> --
> Sincerely yours,
> Mike.
>