1 files changed, 77 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5e37bf14ef2..0bd8c766583 100644
--- a/arch/powerpc/kernel/irq.c
+++ b/arch/powerpc/kernel/irq.c
@@ -64,8 +64,9 @@
 #include <asm/ptrace.h>
 #include <asm/machdep.h>
 #include <asm/udbg.h>
-#ifdef CONFIG_PPC_ISERIES
+#ifdef CONFIG_PPC64
 #include <asm/paca.h>
+#include <asm/firmware.h>
 #endif
 
 int __irq_offset_value;
@@ -95,6 +96,74 @@ extern atomic_t ipi_sent;
 EXPORT_SYMBOL(irq_desc);
 
 int distribute_irqs = 1;
+
+static inline unsigned long get_hard_enabled(void)
+{
+	unsigned long enabled;
+
+	__asm__ __volatile__("lbz %0,%1(13)"
+	: "=r" (enabled) : "i" (offsetof(struct paca_struct, hard_enabled)));
+
+	return enabled;
+}
+
+static inline void set_soft_enabled(unsigned long enable)
+{
+	__asm__ __volatile__("stb %0,%1(13)"
+	: : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled)));
+}
+
+void local_irq_restore(unsigned long en)
+{
+	/*
+	 * get_paca()->soft_enabled = en;
+	 * Is it ever valid to use local_irq_restore(0) when soft_enabled is 1?
+	 * That was allowed before, and in such a case we do need to take care
+	 * that gcc will set soft_enabled directly via r13, not choose to use
+	 * an intermediate register, lest we're preempted to a different cpu.
+	 */
+	set_soft_enabled(en);
+	if (!en)
+		return;
+
+	if (firmware_has_feature(FW_FEATURE_ISERIES)) {
+		/*
+		 * Do we need to disable preemption here?  Not really: in the
+		 * unlikely event that we're preempted to a different cpu in
+		 * between getting r13, loading its lppaca_ptr, and loading
+		 * its any_int, we might call iseries_handle_interrupts without
+		 * an interrupt pending on the new cpu, but that's no disaster,
+		 * is it?  And the business of preempting us off the old cpu
+		 * would itself involve a local_irq_restore which handles the
+		 * interrupt to that cpu.
+		 *
+		 * But use "local_paca->lppaca_ptr" instead of "get_lppaca()"
+		 * to avoid any preemption checking added into get_paca().
+		 */
+		if (local_paca->lppaca_ptr->int_dword.any_int)
+			iseries_handle_interrupts();
+		return;
+	}
+
+	/*
+	 * if (get_paca()->hard_enabled) return;
+	 * But again we need to take care that gcc gets hard_enabled directly
+	 * via r13, not choose to use an intermediate register, lest we're
+	 * preempted to a different cpu in between the two instructions.
+	 */
+	if (get_hard_enabled())
+		return;
+
+	/*
+	 * Need to hard-enable interrupts here.  Since currently disabled,
+	 * no need to take further asm precautions against preemption; but
+	 * use local_paca instead of get_paca() to avoid preemption checking.
+	 */
+	local_paca->hard_enabled = en;
+	if ((int)mfspr(SPRN_DEC) < 0)
+		mtspr(SPRN_DEC, 1);
+	hard_irq_enable();
+}
 #endif /* CONFIG_PPC64 */
 
 int show_interrupts(struct seq_file *p, void *v)
@@ -246,7 +315,8 @@ void do_IRQ(struct pt_regs *regs)
 	set_irq_regs(old_regs);
 
 #ifdef CONFIG_PPC_ISERIES
-	if (get_lppaca()->int_dword.fields.decr_int) {
+	if (firmware_has_feature(FW_FEATURE_ISERIES) &&
+			get_lppaca()->int_dword.fields.decr_int) {
 		get_lppaca()->int_dword.fields.decr_int = 0;
 		/* Signal a fake decrementer interrupt */
 		timer_interrupt(regs);
@@ -626,10 +696,14 @@ EXPORT_SYMBOL_GPL(irq_of_parse_and_map);
 
 void irq_dispose_mapping(unsigned int virq)
 {
-	struct irq_host *host = irq_map[virq].host;
+	struct irq_host *host;
 	irq_hw_number_t hwirq;
 	unsigned long flags;
 
+	if (virq == NO_IRQ)
+		return;
+
+	host = irq_map[virq].host;
 	WARN_ON (host == NULL);
 	if (host == NULL)
 		return;