target/ppc: trigger PERFM EBBs from power8-pmu.c

target/ppc: trigger PERFM EBBs from power8-pmu.c

This patch adds the EBB exception support that are triggered by
Performance Monitor alerts. This happens when a Performance Monitor
alert occurs and MMCR0_EBE, BESCR_PME and BESCR_GE are set.

fire_PMC_interrupt() will execute the raise_ebb_perfm_exception() helper
which will check for MMCR0_EBE, BESCR_PME and BESCR_GE bits. If all bits
are set, do_ebb() will attempt to trigger a PERFM EBB event.

If the EBB facility is enabled in both FSCR and HFSCR we consider that
the EBB is valid and set BESCR_PMEO. After that, if we're running in
problem state, fire a POWERPC_EXCP_PERM_EBB immediately. Otherwise we'll
queue a PPC_INTERRUPT_EBB.

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220225101140.1054160-5-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>