target/arm: kvm: Handle DABT with no valid ISS

target/arm: kvm: Handle DABT with no valid ISS

On ARMv7 & ARMv8 some load/store instructions might trigger a data abort
exception with no valid ISS info to be decoded. The lack of decode info
makes it at least tricky to emulate those instruction which is one of the
(many) reasons why KVM will not even try to do so.

Add support for handling those by requesting KVM to inject external
dabt into the quest.

Signed-off-by: Beata Michalska <beata.michalska@linaro.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-id: 20200629114110.30723-2-beata.michalska@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>