Supercedes: 20230914174436.1597356-1-richard.henderson@linaro.org
("[PATCH 0/6] accel/tcg: Always require can_do_io (#1866)")
An alternate fix for #1866 without touching can_do_io, and is
perhaps a bit cleaner and clearer.
Instead, the current cpu checks whether an address space update
is required on each entry to the slow path. This certainly
catches all i/o. It easily works for the sequential case of
two i/o, the first of which changes the address space and the
second of which requires the new address space.
I've done a tiny bit of performance testing between the two
solutions and it seems to be a wash. So now it's simply a
matter of cleanliness.