linux-kernel - Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (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] [day] [month] [year] [list]

Message-ID: <Z7dbxJNxlW2EA_aa@tuxmaker.boeblingen.de.ibm.com>
Date: Thu, 20 Feb 2025 17:43:48 +0100
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Dave Young <dyoung@...hat.com>
Cc: Alexander Graf <graf@...zon.com>, Mike Rapoport <rppt@...nel.org>,
        linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Anthony Yznaga <anthony.yznaga@...cle.com>,
        Arnd Bergmann <arnd@...db.de>, Ashish Kalra <ashish.kalra@....com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Eric Biederman <ebiederm@...ssion.com>, Ingo Molnar <mingo@...hat.com>,
        James Gowans <jgowans@...zon.com>, Jonathan Corbet <corbet@....net>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Pratyush Yadav <ptyadav@...zon.de>, Rob Herring <robh+dt@...nel.org>,
        Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>,
        Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        Usama Arif <usama.arif@...edance.com>, Will Deacon <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, Philipp Rudo <prudo@...hat.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>, linux-s390@...r.kernel.org
Subject: Re: [PATCH v4 00/14] kexec: introduce Kexec HandOver (KHO)

On Thu, Feb 20, 2025 at 09:49:52AM +0800, Dave Young wrote:
> On Wed, 19 Feb 2025 at 21:55, Alexander Graf <graf@...zon.com> wrote:
> > >>> What architecture exactly does this KHO work fine?   Device Tree
> > >>> should be ok on arm*, x86 and power*, but how about s390?
> > >> KHO does not use device tree as the boot protocol, it uses FDT as a data
> > >> structure and adds architecture specific bits to the boot structures to
> > >> point to that data, very similar to how IMA_KEXEC works.
> > >>
> > >> Currently KHO is implemented on arm64 and x86, but there is no fundamental
> > >> reason why it wouldn't work on any architecture that supports kexec.
> > > Well,  the problem is whether there is a way to  add dtb in the early
> > > boot path,  for X86 it is added via setup_data,  if there is no such
> > > way I'm not sure if it is doable especially for passing some info for
> > > early boot use.  Then the KHO will be only for limited use cases.
> >
> >
> > Every architecture has a platform specific way of passing data into the
> > kernel so it can find its command line and initrd. S390x for example has
> > struct parmarea. To enable s390x, you would remove some of its padding
> > and replace it with a KHO base addr + size, so that the new kernel can
> > find the KHO state tree.
> 
> Ok, thanks for the info,  I cced s390 people maybe they can provide inputs.

If I understand correctly, the parmarea would be used for passing the
FDT address - which appears to be fine. However, s390 does not implement
early_memremap()/early_memunmap(), which KHO needs.

Thanks, Dave!