Re: [RFC PATCH] docs/about/deprecated: Deprecate 32-bit host systems

On 04/04/2023 17.42, BALATON Zoltan wrote: > On Tue, 4 Apr 2023, Cédric Le Goater wrote: >> [ adding Zoltan ] >> >> On 4/4/23 16:00, Thomas Huth wrote: >>> On 05/02/2023 23.12, Mark Cave-Ayland wrote: >>>> On 30/01/2023 20:45, Alex Bennée wrote: >>>> >>>>> Daniel P. Berrangé <berrange(a)redhat.com&gt; writes: >>>>> >>>>>> On Mon, Jan 30, 2023 at 11:47:02AM +0000, Peter Maydell wrote: >>>>>>> On Mon, 30 Jan 2023 at 11:44, Thomas Huth <thuth(a)redhat.com&gt; wrote: >>>>>>>> >>>>>>>> Testing 32-bit host OS support takes a lot of precious time during >>>>>>>> the QEMU >>>>>>>> contiguous integration tests, and considering that many OS vendors >>>>>>>> stopped >>>>>>>> shipping 32-bit variants of their OS distributions and most hardware >>>>>>>> from >>>>>>>> the past >10 years is capable of 64-bit >>>>>>> >>>>>>> True for x86, not necessarily true for other architectures. >>>>>>> Are you proposing to deprecate x86 32-bit, or all 32-bit? >>>>>>> I'm not entirely sure about whether we're yet at a point where >>>>>>> I'd want to deprecate-and-drop 32-bit arm host support. >>>>>> >>>>>> Do we have a feeling on which aspects of 32-bit cause us the support >>>>>> burden ? The boring stuff like compiler errors from mismatched integer >>>>>> sizes is mostly quick & easy to detect simply through a cross compile. >>>>>> >>>>>> I vaguely recall someone mentioned problems with atomic ops in the >>>>>> past, >>>>>> or was it 128-bit ints, caused implications for the codebase ? >>>>> >>>>> Atomic operations on > TARGET_BIT_SIZE and cputlb when >>>>> TCG_OVERSIZED_GUEST is set. Also the core TCG code and a bunch of the >>>>> backends have TARGET_LONG_BITS > TCG_TARGET_REG_BITS ifdefs peppered >>>>> throughout. >>>> >>>> I am one of an admittedly small group of people still interested in >>>> using KVM-PR on ppc32 to boot MacOS, although there is some interest on >>>> using 64-bit KVM-PR to run super-fast MacOS on modern Talos hardware. >>>> >>>>  From my perspective losing the ability to run 64-bit guests on 32-bit >>>> hardware with TCG wouldn't be an issue, as long as it were still >>>> possible to use qemu-system-ppc on 32-bit hardware using both TCG and >>>> KVM to help debug the remaining issues. >>> >>>   Hi Mark! >>> >>> Just out of curiosity (since we briefly talked about 32-bit KVM on ppc in >>> today's QEMU/KVM call - in the context of whether qemu-system-ppc64 is a >>> proper superset of qemu-system-ppc when it comes to building a unified >>> qemu-system binary): What host machine are you using for running KVM-PR? >>> And which QEMU machine are you using for running macOS? The mac99 or the >>> g3beige machine? >> >> Zoltan, what about the pegasos2 and sam460ex machines ? can they be run >> under KVM ? > > I don't know as I don't have PPC hardware to test on but theoretically they > should work. Although BookE KVM was dropped from Linux I think so sam460ex > could only work with an old kernel on a BookE host which is now rare [...] Thanks for your explanations, that indeed helps to understand the situation! But are you sure about the BookE KVM removal in the Linux kernel? ... when I look at the arch/powerpc/kvm/ folder there, I can still see some files there with "booke" in the name?