ppc64: revised machine check exception handler

arch/ppc64/kernel/traps.c

@@ -151,30 +151,67 @@ SystemResetException(struct pt_regs *regs)
 	/* What should we do here? We could issue a shutdown or hard reset. */
 }
 
-static int power4_handle_mce(struct pt_regs *regs)
+/* 
+ * See if we can recover from a machine check exception.
+ * This is only called on power4 (or above) and only via
+ * the Firmware Non-Maskable Interrupts (fwnmi) handler
+ * which provides the error analysis for us.
+ *
+ * Return 1 if corrected (or delivered a signal).
+ * Return 0 if there is nothing we can do.
+ */
+static int recover_mce(struct pt_regs *regs, struct rtas_error_log err)
 {
+	siginfo_t info;
+
+	if (err.disposition == DISP_FULLY_RECOVERED) {
+		/* Platform corrected itself */
+		return 1;
+	} else if ((regs->msr & MSR_RI) &&
+		   user_mode(regs) &&
+		   err.severity == SEVERITY_ERROR_SYNC &&
+		   err.disposition == DISP_NOT_RECOVERED &&
+		   err.target == TARGET_MEMORY &&
+		   err.type == TYPE_ECC_UNCORR &&
+		   !(current->pid == 0 || current->pid == 1)) {
+		/* Kill off a user process with an ECC error */
+		info.si_signo = SIGBUS;
+		info.si_errno = 0;
+		/* XXX something better for ECC error? */
+		info.si_code = BUS_ADRERR;
+		info.si_addr = (void *)regs->nip;
+		printk(KERN_ERR "MCE: uncorrectable ecc error for pid %d\n",
+		       current->pid);
+		_exception(SIGBUS, &info, regs);
+		return 1;
+	}
 	return 0;
 }
 
+/*
+ * Handle a machine check.
+ *
+ * Note that on Power 4 and beyond Firmware Non-Maskable Interrupts (fwnmi)
+ * should be present.  If so the handler which called us tells us if the
+ * error was recovered (never true if RI=0).
+ *
+ * On hardware prior to Power 4 these exceptions were asynchronous which
+ * means we can't tell exactly where it occurred and so we can't recover.
+ *
+ * Note that the debugger should test RI=0 and warn the user that system
+ * state has been corrupted.
+ */
 void
 MachineCheckException(struct pt_regs *regs)
 {
-	siginfo_t info;
+	struct rtas_error_log err, *errp;
 
 	if (fwnmi_active) {
-		struct rtas_error_log *errhdr = FWNMI_get_errinfo(regs);
-		if (errhdr) {
-			/* ToDo: attempt to recover from some errors here */
-		}
-		FWNMI_release_errinfo();
-	}
-
-	if (!user_mode(regs)) {
-		/* Attempt to recover if the interrupt is recoverable */
-		if (regs->msr & MSR_RI) {
-			if ((__is_processor(PV_POWER4) ||
-			     __is_processor(PV_POWER4p)) &&
-			     power4_handle_mce(regs))
+		errp = FWNMI_get_errinfo(regs);
+		if (errp)
+			err = *errp;
+		FWNMI_release_errinfo();	/* frees errp */
+		if (errp && recover_mce(regs, err))
 			return;
 	}
 
@@ -195,17 +232,6 @@ MachineCheckException(struct pt_regs *regs)
 	bust_spinlocks(0);
 	spin_unlock_irq(&die_lock);
 	panic("Unrecoverable Machine Check");
-	}
-
-	/*
-	 * XXX we should check RI bit on exception exit and kill the
-	 * task if it was cleared
-	 */
-	info.si_signo = SIGBUS;
-	info.si_errno = 0;
-	info.si_code = BUS_ADRERR;
-	info.si_addr = (void *)regs->nip;
-	_exception(SIGSEGV, &info, regs);
 }
 
 void