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

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On Tue, 4 Apr 2023, 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@xxxxxxxxxx> 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@xxxxxxxxxx> 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

Another issue I know is that mac99 behaves differently in qemu-system-ppc and qemu-system-ppc64. This is not only confusing users but makes it more difficult to get rid of qemu-system-ppc. I've tried to solve that and sumbitted a patch to start deprecating these but I could not get that merged. That thread ended here:

https://lists.nongnu.org/archive/html/qemu-ppc/2023-01/msg00406.html

Regards,
BALATON Zoltan

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