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>

target/ppc/cpu.h

@@ -2502,6 +2502,11 @@ void QEMU_NORETURN raise_exception_err(CPUPPCState *env, uint32_t exception,
 void QEMU_NORETURN raise_exception_err_ra(CPUPPCState *env, uint32_t exception,
                                           uint32_t error_code, uintptr_t raddr);
 
+/* PERFM EBB helper*/
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+void raise_ebb_perfm_exception(CPUPPCState *env);
+#endif
+
 #if !defined(CONFIG_USER_ONLY)
 static inline int booke206_tlbm_id(CPUPPCState *env, ppcmas_tlb_t *tlbm)
 {

target/ppc/excp_helper.c

@@ -2066,6 +2066,54 @@ void helper_rfebb(CPUPPCState *env, target_ulong s)
         env->spr[SPR_BESCR] &= ~BESCR_GE;
     }
 }
+
+/*
+ * Triggers or queues an 'ebb_excp' EBB exception. All checks
+ * but FSCR, HFSCR and msr_pr must be done beforehand.
+ *
+ * PowerISA v3.1 isn't clear about whether an EBB should be
+ * postponed or cancelled if the EBB facility is unavailable.
+ * Our assumption here is that the EBB is cancelled if both
+ * FSCR and HFSCR EBB facilities aren't available.
+ */
+static void do_ebb(CPUPPCState *env, int ebb_excp)
+{
+    PowerPCCPU *cpu = env_archcpu(env);
+    CPUState *cs = CPU(cpu);
+
+    /*
+     * FSCR_EBB and FSCR_IC_EBB are the same bits used with
+     * HFSCR.
+     */
+    helper_fscr_facility_check(env, FSCR_EBB, 0, FSCR_IC_EBB);
+    helper_hfscr_facility_check(env, FSCR_EBB, "EBB", FSCR_IC_EBB);
+
+    if (ebb_excp == POWERPC_EXCP_PERFM_EBB) {
+        env->spr[SPR_BESCR] |= BESCR_PMEO;
+    } else if (ebb_excp == POWERPC_EXCP_EXTERNAL_EBB) {
+        env->spr[SPR_BESCR] |= BESCR_EEO;
+    }
+
+    if (msr_pr == 1) {
+        powerpc_excp(cpu, ebb_excp);
+    } else {
+        env->pending_interrupts |= 1 << PPC_INTERRUPT_EBB;
+        cpu_interrupt(cs, CPU_INTERRUPT_HARD);
+    }
+}
+
+void raise_ebb_perfm_exception(CPUPPCState *env)
+{
+    bool perfm_ebb_enabled = env->spr[SPR_POWER_MMCR0] & MMCR0_EBE &&
+                             env->spr[SPR_BESCR] & BESCR_PME &&
+                             env->spr[SPR_BESCR] & BESCR_GE;
+
+    if (!perfm_ebb_enabled) {
+        return;
+    }
+
+    do_ebb(env, POWERPC_EXCP_PERFM_EBB);
+}
 #endif
 
 /*****************************************************************************/

target/ppc/power8-pmu.c

@@ -307,8 +307,7 @@ static void fire_PMC_interrupt(PowerPCCPU *cpu)
         env->spr[SPR_POWER_MMCR0] |= MMCR0_PMAO;
     }
 
-    /* PMC interrupt not implemented yet */
+    raise_ebb_perfm_exception(env);
-    return;
 }
 
 /* This helper assumes that the PMC is running. */