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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On 5/11/26 18:38, David Woodhouse wrote: > Not *everything* is in CPUID; one recent exception that comes to mind > is the SUPPRESS_EOI_BROADCAST quirk. But on x86 we preserve the > existing behaviour of older kernels — even when that behaviour doesn't > make much sense, as with SUPPRESS_EOI_BROADCAST where older KVM would > *advertise* the feature, but not actually *implement* it. Nevertheless, > that remains the default behaviour of future kernels unless userspace > explicitly opts in to fully enable (or disable) the feature. > > But this documentation update isn't even asking for that compatible-by- > default behaviour, even though that is the right thing to do. It's only > asking that it be *possible* to reinstate the old behaviour, for > userspace that *knows* about the change and explicitly wants to go back > to the old way to remain compatible. Yep, these are the "quirks"---if it's too early for Arm to commit to that, I guess it's fine. However, independent of this patch which I (obviously) believe is a good idea, I'd like to understand how far it is, assuming 1) no quirks 2) same CPU host. By the way, you didn't Cc Marc... Paolo