1 files changed, 77 insertions, 3 deletions

diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c
index 5e37bf14ef2d..0bd8c7665834 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;