[Qemu-devel] [PATCH] hw/intc/arm_gic: add tracepoints

[Qemu-devel] [PATCH] hw/intc/arm_gic: add tracepoints

[Hollis Blanchard]

These are obviously critical to understanding interrupt delivery:
gic_enable_irq
gic_disable_irq
gic_set_irq (inbound irq from device models)
gic_update_set_irq (outbound irq to CPU)
gic_acknowledge_irq

The only one that I think might raise eyebrows is gic_update_bestirq, but I've
(sadly) debugged problems that ended up being caused by unexpected priorities.
Knowing that the GIC has an irq ready, but doesn't deliver to the CPU due to
priority, has also proven important.

Signed-off-by: Hollis Blanchard <hollis_blanchard@mentor.com>
---
 hw/intc/arm_gic.c | 12 ++++++++++++
 trace-events      |  8 ++++++++
 2 files changed, 20 insertions(+)

diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c
index f551241..5ee79b8 100644
--- a/hw/intc/arm_gic.c
+++ b/hw/intc/arm_gic.c
@@ -23,6 +23,7 @@
 #include "gic_internal.h"
 #include "qapi/error.h"
 #include "qom/cpu.h"
+#include "trace.h"
 
 //#define DEBUG_GIC
 
@@ -93,6 +94,11 @@ void gic_update(GICState *s)
             }
         }
 
+        if (best_irq != 1023) {
+            trace_gic_update_bestirq(cpu, best_irq, best_prio,
+                s->priority_mask[cpu], s->running_priority[cpu]);
+        }
+
         irq_level = fiq_level = 0;
 
         if (best_prio < s->priority_mask[cpu]) {
@@ -106,10 +112,12 @@ void gic_update(GICState *s)
                         DPRINTF("Raised pending FIQ %d (cpu %d)\n",
                                 best_irq, cpu);
                         fiq_level = 1;
+                        trace_gic_update_set_irq(cpu, "fiq", fiq_level);
                     } else {
                         DPRINTF("Raised pending IRQ %d (cpu %d)\n",
                                 best_irq, cpu);
                         irq_level = 1;
+                        trace_gic_update_set_irq(cpu, "irq", irq_level);
                     }
                 }
             }
@@ -197,6 +205,7 @@ static void gic_set_irq(void *opaque, int irq, int level)
     } else {
         gic_set_irq_generic(s, irq, level, cm, target);
     }
+    trace_gic_set_irq(irq, level, cm, target);
 
     gic_update(s);
 }
@@ -332,6 +341,7 @@ uint32_t gic_acknowledge_irq(GICState *s, int cpu, MemTxAttrs attrs)
      * is in the wrong group.
      */
     irq = gic_get_current_pending_irq(s, cpu, attrs);
+    trace_gic_acknowledge_irq(cpu, irq);
 
     if (irq >= GIC_MAXIRQ) {
         DPRINTF("ACK, no pending interrupt or it is hidden: %d\n", irq);
@@ -853,6 +863,7 @@ static void gic_dist_writeb(void *opaque, hwaddr offset,
 
                 if (!GIC_TEST_ENABLED(irq + i, cm)) {
                     DPRINTF("Enabled IRQ %d\n", irq + i);
+                    trace_gic_enable_irq(irq + i);
                 }
                 GIC_SET_ENABLED(irq + i, cm);
                 /* If a raised level triggered IRQ enabled then mark
@@ -879,6 +890,7 @@ static void gic_dist_writeb(void *opaque, hwaddr offset,
 
                 if (GIC_TEST_ENABLED(irq + i, cm)) {
                     DPRINTF("Disabled IRQ %d\n", irq + i);
+                    trace_gic_disable_irq(irq + i);
                 }
                 GIC_CLEAR_ENABLED(irq + i, cm);
             }
diff --git a/trace-events b/trace-events
index 8350743..8796ff7 100644
--- a/trace-events
+++ b/trace-events
@@ -1909,3 +1909,11 @@ aspeed_vic_update_fiq(int flags) "Raising FIQ: %d"
 aspeed_vic_update_irq(int flags) "Raising IRQ: %d"
 aspeed_vic_read(uint64_t offset, unsigned size, uint32_t value) "From 0x%" PRIx64 " of size %u: 0x%" PRIx32
 aspeed_vic_write(uint64_t offset, unsigned size, uint32_t data) "To 0x%" PRIx64 " of size %u: 0x%" PRIx32
+
+# hw/intc/arm_gic.c
+gic_enable_irq(int irq) "irq %d enabled"
+gic_disable_irq(int irq) "irq %d disabled"
+gic_set_irq(int irq, int level, int cpumask, int target) "irq %d level %d cpumask 0x%x target 0x%x"
+gic_update_bestirq(int cpu, int irq, int prio, int priority_mask, int running_priority) "cpu %d irq %d priority %d cpu priority mask %d cpu running priority %d"
+gic_update_set_irq(int cpu, const char *name, int level) "cpu[%d]: %s = %d"
+gic_acknowledge_irq(int cpu, int irq) "cpu %d acknowledged irq %d"
-- 
2.5.5

Re: [Qemu-devel] [PATCH] hw/intc/arm_gic: add tracepoints

[Stefan Hajnoczi]

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On Thu, Apr 21, 2016 at 08:24:41AM -0700, Hollis Blanchard wrote:
> These are obviously critical to understanding interrupt delivery:
> gic_enable_irq
> gic_disable_irq
> gic_set_irq (inbound irq from device models)
> gic_update_set_irq (outbound irq to CPU)
> gic_acknowledge_irq
> 
> The only one that I think might raise eyebrows is gic_update_bestirq, but I've
> (sadly) debugged problems that ended up being caused by unexpected priorities.
> Knowing that the GIC has an irq ready, but doesn't deliver to the CPU due to
> priority, has also proven important.
> 
> Signed-off-by: Hollis Blanchard <hollis_blanchard@mentor.com>
> ---
>  hw/intc/arm_gic.c | 12 ++++++++++++
>  trace-events      |  8 ++++++++
>  2 files changed, 20 insertions(+)

Thanks, applied to my tracing tree (for QEMU 2.7):
https://github.com/stefanha/qemu/commits/tracing

Stefan

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