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

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