powerpc/powernv: Machine check exception handling.

Add basic error handling in machine check exception handler.

- If MSR_RI isn't set, we can not recover.
- Check if disposition set to OpalMCE_DISPOSITION_RECOVERED.
- Check if address at fault is inside kernel address space, if not then send
  SIGBUS to process if we hit exception when in userspace.
- If address at fault is not provided then and if we get a synchronous machine
  check while in userspace then kill the task.

Signed-off-by: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/mce.c

@@ -316,3 +316,30 @@ void machine_check_print_event_info(struct machine_check_event *evt)
 		break;
 	}
 }
+
+uint64_t get_mce_fault_addr(struct machine_check_event *evt)
+{
+	switch (evt->error_type) {
+	case MCE_ERROR_TYPE_UE:
+		if (evt->u.ue_error.effective_address_provided)
+			return evt->u.ue_error.effective_address;
+		break;
+	case MCE_ERROR_TYPE_SLB:
+		if (evt->u.slb_error.effective_address_provided)
+			return evt->u.slb_error.effective_address;
+		break;
+	case MCE_ERROR_TYPE_ERAT:
+		if (evt->u.erat_error.effective_address_provided)
+			return evt->u.erat_error.effective_address;
+		break;
+	case MCE_ERROR_TYPE_TLB:
+		if (evt->u.tlb_error.effective_address_provided)
+			return evt->u.tlb_error.effective_address;
+		break;
+	default:
+	case MCE_ERROR_TYPE_UNKNOWN:
+		break;
+	}
+	return 0;
+}
+EXPORT_SYMBOL(get_mce_fault_addr);