hvf: Simplify post reset/init/loadvm hooks

hvf: Simplify post reset/init/loadvm hooks

The hooks we have that call us after reset, init and loadvm really all
just want to say "The reference of all register state is in the QEMU
vcpu struct, please push it".

We already have a working pushing mechanism though called cpu->vcpu_dirty,
so we can just reuse that for all of the above, syncing state properly the
next time we actually execute a vCPU.

This fixes PSCI resets on ARM, as they modify CPU state even after the
post init call has completed, but before we execute the vCPU again.

To also make the scheme work for x86, we have to make sure we don't
move stale eflags into our env when the vcpu state is dirty.

Signed-off-by: Alexander Graf <agraf@csgraf.de>
Reviewed-by: Roman Bolshakov <r.bolshakov@yadro.com>
Tested-by: Roman Bolshakov <r.bolshakov@yadro.com>
Reviewed-by: Sergio Lopez <slp@redhat.com>
Message-id: 20210519202253.76782-13-agraf@csgraf.de
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>