[PATCH v3 15/41] KVM: PPC: Book3S 64: Minimise hcall handler calling convention differences

[Nicholas Piggin]

Excerpts from Nicholas Piggin's message of March 6, 2021 1:06 am:
> This sets up the same calling convention from interrupt entry to
> KVM interrupt handler for system calls as exists for other interrupt
> types.
> 
> This is a better API, it uses a save area rather than SPR, and it has
> more registers free to use. Using a single common API helps maintain
> it, and it becomes easier to use in C in a later patch.

On second look I'm happy enough with this.

It does add some hcall setup code back into exception-64s.S and removes
most of the "fixup" code that was previously moved into 
book3s_64_entry.S in patch 12. But if you take patch 12 and 13 and other
earlier patches together they are moving most KVM interrupt knowledge
into KVM which is a good change.

Once that is done, this final one then gets hcall into better shape for
the C code. If anything this patch could go together with patch 12 but
I guess I ended up writing it for the C code whereas the previous ones
were cleanups so the ordering didn't come out that way. It won't be
trivial to move now so I don't think I'd bother.

Thanks,
Nick