linux-kernel - Re: [RFC 0/5] KVM: drop 32-bit host support on all architectures

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: <6e971322-8b21-4d73-922c-a6032c6fe9bd@app.fastmail.com>
Date: Fri, 13 Dec 2024 09:03:30 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "A. Wilcox" <AWilcox@...cox-tech.com>, "Arnd Bergmann" <arnd@...nel.org>
Cc: kvm@...r.kernel.org, "Thomas Bogendoerfer" <tsbogend@...ha.franken.de>,
 "Huacai Chen" <chenhuacai@...nel.org>,
 "Jiaxun Yang" <jiaxun.yang@...goat.com>,
 "Michael Ellerman" <mpe@...erman.id.au>,
 "Nicholas Piggin" <npiggin@...il.com>,
 "Christophe Leroy" <christophe.leroy@...roup.eu>,
 "Naveen N Rao" <naveen@...nel.org>,
 "Madhavan Srinivasan" <maddy@...ux.ibm.com>,
 "Alexander Graf" <graf@...zon.com>, "Crystal Wood" <crwood@...hat.com>,
 "Anup Patel" <anup@...infault.org>,
 "Atish Patra" <atishp@...shpatra.org>,
 "Paul Walmsley" <paul.walmsley@...ive.com>,
 "Palmer Dabbelt" <palmer@...belt.com>,
 "Albert Ou" <aou@...s.berkeley.edu>,
 "Sean Christopherson" <seanjc@...gle.com>,
 "Paolo Bonzini" <pbonzini@...hat.com>,
 "Thomas Gleixner" <tglx@...utronix.de>, "Ingo Molnar" <mingo@...hat.com>,
 "Borislav Petkov" <bp@...en8.de>,
 "Dave Hansen" <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>,
 "Vitaly Kuznetsov" <vkuznets@...hat.com>,
 "David Woodhouse" <dwmw2@...radead.org>, "Paul Durrant" <paul@....org>,
 "Marc Zyngier" <maz@...nel.org>, linux-kernel@...r.kernel.org,
 linux-mips@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 kvm-riscv@...ts.infradead.org, linux-riscv@...ts.infradead.org
Subject: Re: [RFC 0/5] KVM: drop 32-bit host support on all architectures

On Fri, Dec 13, 2024, at 04:51, A. Wilcox wrote:
> On Dec 12, 2024, at 6:55 AM, Arnd Bergmann <arnd@...nel.org> wrote:
>> From: Arnd Bergmann <arnd@...db.de>
>> 
>> I submitted a patch to remove KVM support for x86-32 hosts earlier
>> this month, but there were still concerns that this might be useful for
>> testing 32-bit host in general, as that remains supported on three other
>> architectures. I have gone through those three now and prepared similar
>> patches, as all of them seem to be equally obsolete.
>> 
>> Support for 32-bit KVM host on Arm hardware was dropped back in 2020
>> because of lack of users, despite Cortex-A7/A15/A17 based SoCs being
>> much more widely deployed than the other virtualization capable 32-bit
>> CPUs (Intel Core Duo/Silverthorne, PowerPC e300/e500/e600, MIPS P5600)
>> combined.
>
>
> I do use 32-bit KVM on a Core Duo “Yonah” and a Power Mac G4 (MDD), for
> purposes of bisecting kernel issues without having to reboot the host
> machine (when it can be duplicated in a KVM environment).
>
> I suppose it would still be possible to run the hosts on 6.12 LTS for
> some time with newer guests, but it would be unfortunate.

Would it be an option for you to just test those kernels on 64-bit
machines? I assume you prefer to do native builds on 32-bit hardware
because that fits your workflow, but once you get into debugging
in a virtual machine, the results should generally be the same when
building and running on a 64-bit host for both x86-32 and ppc32-classic,
right?

      Arnd