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Fri, 13 Dec 2024 00:20:09 -0800 (PST) X-Google-Smtp-Source: AGHT+IFrCHiXBGnM5x0F9+IJDtAVhPlkiWHtx4O9ovcSIL7K/Npye3omEspq5dEzagyGc9xjVrwPFg== X-Received: by 2002:a05:6000:1a8e:b0:386:32ea:e70d with SMTP id ffacd0b85a97d-3888e0ba2f4mr910591f8f.50.1734078008749; Fri, 13 Dec 2024 00:20:08 -0800 (PST) Received: from [192.168.10.3] ([151.81.118.45]) by smtp.googlemail.com with ESMTPSA id 5b1f17b1804b1-4362559ed8dsm42786805e9.23.2024.12.13.00.20.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 13 Dec 2024 00:20:08 -0800 (PST) Message-ID: <79b9abfe-cfb8-4ef0-8a4b-7b87787e6549@redhat.com> Date: Fri, 13 Dec 2024 09:20:05 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC 0/5] KVM: drop 32-bit host support on all architectures To: Arnd Bergmann , "A. Wilcox" , Arnd Bergmann Cc: kvm@vger.kernel.org, Thomas Bogendoerfer , Huacai Chen , Jiaxun Yang , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Naveen N Rao , Madhavan Srinivasan , Alexander Graf , Crystal Wood , Anup Patel , Atish Patra , Paul Walmsley , Palmer Dabbelt , Albert Ou , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Vitaly Kuznetsov , David Woodhouse , Paul Durrant , Marc Zyngier , linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org References: <20241212125516.467123-1-arnd@kernel.org> <35E5C2A3-94AC-446B-A0A1-84B043DBC890@Wilcox-Tech.com> <6e971322-8b21-4d73-922c-a6032c6fe9bd@app.fastmail.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; keydata= xsEhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAc0j UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT7CwU0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSTOwE0EVEJx7gEIAMeHcVzuv2bp9HlWDp6+RkZe+vtl KwAHplb/WH59j2wyG8V6i33+6MlSSJMOFnYUCCL77bucx9uImI5nX24PIlqT+zasVEEVGSRF m8dgkcJDB7Tps0IkNrUi4yof3B3shR+vMY3i3Ip0e41zKx0CvlAhMOo6otaHmcxr35sWq1Jk tLkbn3wG+fPQCVudJJECvVQ//UAthSSEklA50QtD2sBkmQ14ZryEyTHQ+E42K3j2IUmOLriF dNr9NvE1QGmGyIcbw2NIVEBOK/GWxkS5+dmxM2iD4Jdaf2nSn3jlHjEXoPwpMs0KZsgdU0pP JQzMUMwmB1wM8JxovFlPYrhNT9MAEQEAAcLBMwQYAQIACQUCVEJx7gIbDAAKCRB+FRAMzTZp sadRDqCctLmYICZu4GSnie4lKXl+HqlLanpVMOoFNnWs9oRP47MbE2wv8OaYh5pNR9VVgyhD OG0AU7oidG36OeUlrFDTfnPYYSF/mPCxHttosyt8O5kabxnIPv2URuAxDByz+iVbL+RjKaGM GDph56ZTswlx75nZVtIukqzLAQ5fa8OALSGum0cFi4ptZUOhDNz1onz61klD6z3MODi0sBZN Aj6guB2L/+2ZwElZEeRBERRd/uommlYuToAXfNRdUwrwl9gRMiA0WSyTb190zneRRDfpSK5d usXnM/O+kr3Dm+Ui+UioPf6wgbn3T0o6I5BhVhs4h4hWmIW7iNhPjX1iybXfmb1gAFfjtHfL xRUr64svXpyfJMScIQtBAm0ihWPltXkyITA92ngCmPdHa6M1hMh4RDX+Jf1fiWubzp1voAg0 JBrdmNZSQDz0iKmSrx8xkoXYfA3bgtFN8WJH2xgFL28XnqY4M6dLhJwV3z08tPSRqYFm4NMP dRsn0/7oymhneL8RthIvjDDQ5ktUjMe8LtHr70OZE/TT88qvEdhiIVUogHdo4qBrk41+gGQh b906Dudw5YhTJFU3nC6bbF2nrLlB4C/XSiH76ZvqzV0Z/cAMBo5NF/w= In-Reply-To: <6e971322-8b21-4d73-922c-a6032c6fe9bd@app.fastmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 12/13/24 09:03, Arnd Bergmann wrote: > On Fri, Dec 13, 2024, at 04:51, A. Wilcox wrote: >> On Dec 12, 2024, at 6:55 AM, Arnd Bergmann wrote: >>> From: Arnd Bergmann >>> >>> 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? Certainly for x86-32; ppc32 should be able to use PR-state (aka trap and emulate) KVM on a 64-bit host but it's a bit more picky. Another possibility for ppc32 is just emulation with QEMU. Paolo