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

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Message-Id: <35E5C2A3-94AC-446B-A0A1-84B043DBC890@Wilcox-Tech.com>
Date: Thu, 12 Dec 2024 21:51:26 -0600
From: "A. Wilcox" <AWilcox@...cox-Tech.com>
To: Arnd Bergmann <arnd@...nel.org>
Cc: kvm@...r.kernel.org,
 Arnd Bergmann <arnd@...db.de>,
 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 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.

Best,
-arw

> 
> It probably makes sense to drop all of these at the same time, provided
> there are no actual users remaining (not counting regression testing
> that developers might be doing). Please let me know if you are still
> using any of these machines, or think there needs to be deprecation
> phase first.
> 
>      Arnd

--
Anna Wilcox (she/her)
SW Engineering: C++/Rust, DevOps, POSIX, Py/Ruby
Wilcox Technologies Inc.  |  Adélie Linux