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

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.