powerpc/mm/hash: hard disable irq in the SLB insert path

index 66577cc66dc9..27f5b81c372a 100644
@@ -352,6 +352,14 @@ static void insert_slb_entry(unsigned long vsid, unsigned long ea,
 	/*
 	 * We are irq disabled, hence should be safe to access PACA.
 	 */
+	VM_WARN_ON(!irqs_disabled());
+
+	/*
+	 * We can't take a PMU exception in the following code, so hard
+	 * disable interrupts.
+	 */
+	hard_irq_disable();
+
 	index = get_paca()->stab_rr;
 
 	/*

@@ -369,6 +377,11 @@ static void insert_slb_entry(unsigned long vsid, unsigned long ea,
 		    ((unsigned long) ssize << SLB_VSID_SSIZE_SHIFT);
 	esid_data = mk_esid_data(ea, ssize, index);
 
+	/*
+	 * No need for an isync before or after this slbmte. The exception
+	 * we enter with and the rfid we exit with are context synchronizing.
+	 * Also we only handle user segments here.
+	 */
 	asm volatile("slbmte %0, %1" : : "r" (vsid_data), "r" (esid_data)
 		     : "memory");