The current logic is only considering event-based exceptions triggered
by the performance monitor. This is true now, but we might want to add
support for external event-based exceptions in the future.
Let's make it a bit easier to do so by adding the bit logic that would
happen in case we were dealing with an external event-based exception.
While we're at it, add a few comments explaining why we're setting and
clearing BESCR bits.
Signed-off-by: Daniel Henrique Barboza
---
target/ppc/excp_helper.c | 45 ++--
1 file changed, 39 insertions(+), 6 deletions(-)
diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index a26d266fe6..42e2fee9c8 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -801,14 +801,47 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int
excp_model, int excp)
break;
case POWERPC_EXCP_EBB: /* Event-based branch exception */
if ((env->spr[SPR_FSCR] & (1ull << FSCR_EBB)) &&
-(env->spr[SPR_BESCR] & BESCR_GE) &&
-(env->spr[SPR_BESCR] & BESCR_PME)) {
+(env->spr[SPR_BESCR] & BESCR_GE)) {
target_ulong nip;
-env->spr[SPR_BESCR] &= ~BESCR_GE; /* Clear GE */
-env->spr[SPR_BESCR] |= BESCR_PMEO; /* Set PMEO */
-env->spr[SPR_EBBRR] = env->nip; /* Save NIP for rfebb insn */
-nip = env->spr[SPR_EBBHR]; /* EBB handler */
+/*
+ * If we have Performance Monitor Event-Based exception
+ * enabled (BESCR_PME) and a Performance Monitor alert
+ * occurred (MMCR0_PMAO), clear BESCR_PME and set BESCR_PMEO
+ * (Performance Monitor Event-Based Exception Occurred).
+ *
+ * Software is responsible for clearing both BESCR_PMEO and
+ * MMCR0_PMAO after the event has been handled.
+ */
+if ((env->spr[SPR_BESCR] & BESCR_PME) &&
+(env->spr[SPR_POWER_MMCR0] & MMCR0_PMAO)) {
+env->spr[SPR_BESCR] &= ~BESCR_PME;
+env->spr[SPR_BESCR] |= BESCR_PMEO;
+}
+
+/*
+ * In the case of External Event-Based exceptions, do a
+ * similar logic with BESCR_EE and BESCR_EEO. BESCR_EEO must
+ * also be cleared by software.
+ *
+ * PowerISA 3.1 considers that we'll not have BESCR_PMEO and
+ * BESCR_EEO set at the same time. We can check for BESCR_PMEO
+ * being not set in step above to see if this exception was
+ * trigged by an external event.
+ */
+if (env->spr[SPR_BESCR] & BESCR_EE &&
+!(env->spr[SPR_BESCR] & BESCR_PMEO)) {
+env->spr[SPR_BESCR] &= ~BESCR_EE;
+env->spr[SPR_BESCR] |= BESCR_EEO;
+}
+
+/*
+ * Clear BESCR_GE, save NIP for 'rfebb' and point the
+ * execution to the event handler (SPR_EBBHR) address.
+ */
+env->spr[SPR_BESCR] &= ~BESCR_GE;
+env->spr[SPR_EBBRR] = env->nip;
+nip = env->spr[SPR_EBBHR];
powerpc_set_excp_state(cpu, nip, env->msr);
}
/*
--
2.31.1
