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
