powerpc/64: Replay hypervisor maintenance interrupt first

The HMI (Hypervisor Maintenance Interrupt) is defined by the
architecture to be higher priority than other maskable interrupts, so
replay it first, as a best-effort to replay according to hardware
priorities.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/irq.c

@@ -156,6 +156,15 @@ notrace unsigned int __check_irq_replay(void)
 		lv1_get_version_info(&tmp, &tmp2);
 	}
 
+	/*
+	 * Check if an hypervisor Maintenance interrupt happened.
+	 * This is a higher priority interrupt than the others, so
+	 * replay it first.
+	 */
+	local_paca->irq_happened &= ~PACA_IRQ_HMI;
+	if (happened & PACA_IRQ_HMI)
+		return 0xe60;
+
 	/*
 	 * We may have missed a decrementer interrupt. We check the
 	 * decrementer itself rather than the paca irq_happened field
@@ -191,11 +200,6 @@ notrace unsigned int __check_irq_replay(void)
 	}
 #endif /* CONFIG_PPC_BOOK3E */
 
-	/* Check if an hypervisor Maintenance interrupt happened */
-	local_paca->irq_happened &= ~PACA_IRQ_HMI;
-	if (happened & PACA_IRQ_HMI)
-		return 0xe60;
-
 	/* There should be nothing left ! */
 	BUG_ON(local_paca->irq_happened != 0);