[RFC PATCH] Disable Book-E KVM support?

[Crystal Wood]

On Mon, 2022-11-28 at 14:36 +1000, Nicholas Piggin wrote:
> BookE KVM is in a deep maintenance state, I'm not sure how much testing
> it gets. I don't have a test setup, and it does not look like QEMU has
> any HV architecture enabled. It hasn't been too painful but there are
> some cases where it causes a bit of problem not being able to test, e.g.,
> 
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-November/251452.html
> 
> Time to begin removal process, or are there still people using it? I'm
> happy to to keep making occasional patches to try keep it going if
> there are people testing upstream. Getting HV support into QEMU would
> help with long term support, not sure how big of a job that would be.

Not sure what you mean about QEMU not having e500 HV support?  I don't know if
it's bitrotted, but it's there.

I don't know whether anyone is still using this, but if they are, it's
probably e500mc and not e500v2 (which involved a bunch of hacks to get almost-
sorta-usable performance out of hardware not designed for virtualization).  I
do see that there have been a few recent patches on QEMU e500 (beyond the
treewide cleanup type stuff), though I don't know if they're using KVM.  CCing
them and the QEMU list.

I have an e6500 I could occasionally test on, if it turns out people do still
care about this.  Don't count me as the use case, though. :-)

FWIW, as far as the RECONCILE_IRQ_STATE issue, that used to be done in
kvmppc_handle_exit(), but was moved in commit 9bd880a2c882 to be "cleaner and
faster". :-P

-Crystal