powerpc fixes for 5.11 #6

One fix for a bug in our soft interrupt masking, which could lead to interrupt
 replaying recursing, causing spurious interrupts.
 
 Thanks to:
   Nicholas Piggin.
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Merge tag 'powerpc-5.11-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fix from Michael Ellerman:
 "One fix for a bug in our soft interrupt masking, which could lead to
  interrupt replaying recursing, causing spurious interrupts.

  Thanks to Nicholas Piggin"

* tag 'powerpc-5.11-6' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/64s: prevent recursive replay_soft_interrupts causing superfluous interrupt

arch/powerpc/kernel/irq.c

@@ -180,14 +180,19 @@ void notrace restore_interrupts(void)
 
 void replay_soft_interrupts(void)
 {
-	/*
-	 * We use local_paca rather than get_paca() to avoid all
-	 * the debug_smp_processor_id() business in this low level
-	 * function
-	 */
-	unsigned char happened = local_paca->irq_happened;
 	struct pt_regs regs;
 
+	/*
+	 * Be careful here, calling these interrupt handlers can cause
+	 * softirqs to be raised, which they may run when calling irq_exit,
+	 * which will cause local_irq_enable() to be run, which can then
+	 * recurse into this function. Don't keep any state across
+	 * interrupt handler calls which may change underneath us.
+	 *
+	 * We use local_paca rather than get_paca() to avoid all the
+	 * debug_smp_processor_id() business in this low level function.
+	 */
+
 	ppc_save_regs(&regs);
 	regs.softe = IRQS_ENABLED;
 
@@ -209,7 +214,7 @@ again:
 	 * This is a higher priority interrupt than the others, so
 	 * replay it first.
 	 */
-	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && (happened & PACA_IRQ_HMI)) {
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && (local_paca->irq_happened & PACA_IRQ_HMI)) {
 		local_paca->irq_happened &= ~PACA_IRQ_HMI;
 		regs.trap = 0xe60;
 		handle_hmi_exception(&regs);
@@ -217,7 +222,7 @@ again:
 			hard_irq_disable();
 	}
 
-	if (happened & PACA_IRQ_DEC) {
+	if (local_paca->irq_happened & PACA_IRQ_DEC) {
 		local_paca->irq_happened &= ~PACA_IRQ_DEC;
 		regs.trap = 0x900;
 		timer_interrupt(&regs);
@@ -225,7 +230,7 @@ again:
 			hard_irq_disable();
 	}
 
-	if (happened & PACA_IRQ_EE) {
+	if (local_paca->irq_happened & PACA_IRQ_EE) {
 		local_paca->irq_happened &= ~PACA_IRQ_EE;
 		regs.trap = 0x500;
 		do_IRQ(&regs);
@@ -233,7 +238,7 @@ again:
 			hard_irq_disable();
 	}
 
-	if (IS_ENABLED(CONFIG_PPC_DOORBELL) && (happened & PACA_IRQ_DBELL)) {
+	if (IS_ENABLED(CONFIG_PPC_DOORBELL) && (local_paca->irq_happened & PACA_IRQ_DBELL)) {
 		local_paca->irq_happened &= ~PACA_IRQ_DBELL;
 		if (IS_ENABLED(CONFIG_PPC_BOOK3E))
 			regs.trap = 0x280;
@@ -245,7 +250,7 @@ again:
 	}
 
 	/* Book3E does not support soft-masking PMI interrupts */
-	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && (happened & PACA_IRQ_PMI)) {
+	if (IS_ENABLED(CONFIG_PPC_BOOK3S) && (local_paca->irq_happened & PACA_IRQ_PMI)) {
 		local_paca->irq_happened &= ~PACA_IRQ_PMI;
 		regs.trap = 0xf00;
 		performance_monitor_exception(&regs);
@@ -253,8 +258,7 @@ again:
 			hard_irq_disable();
 	}
 
-	happened = local_paca->irq_happened;
+	if (local_paca->irq_happened & ~PACA_IRQ_HARD_DIS) {
-	if (happened & ~PACA_IRQ_HARD_DIS) {
 		/*
 		 * We are responding to the next interrupt, so interrupt-off
 		 * latencies should be reset here.