[PATCH v2 1/3] arm_gic: Mask the un-supported priority bits

[Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>]

Priority bits implemented in arm-gic can be 8 to 4, un-implemented bits
are read as zeros(RAZ).

Signed-off-by: Sai Pavan Boddu <sai.pavan.boddu@xilinx.com>
---
 hw/intc/arm_gic.c                | 26 ++++++++++++++++++++++++--
 hw/intc/arm_gic_common.c         |  1 +
 include/hw/intc/arm_gic_common.h |  1 +
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c
index 1d7da7b..dec8767 100644
--- a/hw/intc/arm_gic.c
+++ b/hw/intc/arm_gic.c
@@ -641,6 +641,23 @@ uint32_t gic_acknowledge_irq(GICState *s, int cpu, MemTxAttrs attrs)
     return ret;
 }
 
+static uint32_t gic_fullprio_mask(GICState *s, int cpu)
+{
+    /*
+     * Return a mask word which clears the unimplemented priority
+     * bits from a priority value for an interrupt. (Not to be
+     * confused with the group priority, whose mask depends on BPR.)
+     */
+    int unimpBits;
+
+    if (gic_is_vcpu(cpu)) {
+        unimpBits = GIC_VIRT_MAX_GROUP_PRIO_BITS;
+    } else {
+        unimpBits = 8 - s->n_prio_bits;
+    }
+    return ~0U << unimpBits;
+}
+
 void gic_dist_set_priority(GICState *s, int cpu, int irq, uint8_t val,
                       MemTxAttrs attrs)
 {
@@ -669,7 +686,7 @@ static uint32_t gic_dist_get_priority(GICState *s, int cpu, int irq,
         }
         prio = (prio << 1) & 0xff; /* Non-secure view */
     }
-    return prio;
+    return prio & gic_fullprio_mask(s, cpu);
 }
 
 static void gic_set_priority_mask(GICState *s, int cpu, uint8_t pmask,
@@ -684,7 +701,7 @@ static void gic_set_priority_mask(GICState *s, int cpu, uint8_t pmask,
             return;
         }
     }
-    s->priority_mask[cpu] = pmask;
+    s->priority_mask[cpu] = pmask & gic_fullprio_mask(s, cpu);
 }
 
 static uint32_t gic_get_priority_mask(GICState *s, int cpu, MemTxAttrs attrs)
@@ -2055,6 +2072,11 @@ static void arm_gic_realize(DeviceState *dev, Error **errp)
         return;
     }
 
+    if (s->n_prio_bits > 8) {
+        error_setg(errp, "num-priority-bits cannot be greater than 8");
+        return;
+    }
+
     /* This creates distributor, main CPU interface (s->cpuiomem[0]) and if
      * enabled, virtualization extensions related interfaces (main virtual
      * interface (s->vifaceiomem[0]) and virtual CPU interface).
diff --git a/hw/intc/arm_gic_common.c b/hw/intc/arm_gic_common.c
index e6c4fe7..7b44d56 100644
--- a/hw/intc/arm_gic_common.c
+++ b/hw/intc/arm_gic_common.c
@@ -357,6 +357,7 @@ static Property arm_gic_common_properties[] = {
     DEFINE_PROP_BOOL("has-security-extensions", GICState, security_extn, 0),
     /* True if the GIC should implement the virtualization extensions */
     DEFINE_PROP_BOOL("has-virtualization-extensions", GICState, virt_extn, 0),
+    DEFINE_PROP_UINT32("num-priority-bits", GICState, n_prio_bits, 8),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/intc/arm_gic_common.h b/include/hw/intc/arm_gic_common.h
index b5585fe..6e0d6b8 100644
--- a/include/hw/intc/arm_gic_common.h
+++ b/include/hw/intc/arm_gic_common.h
@@ -96,6 +96,7 @@ typedef struct GICState {
     uint16_t priority_mask[GIC_NCPU_VCPU];
     uint16_t running_priority[GIC_NCPU_VCPU];
     uint16_t current_pending[GIC_NCPU_VCPU];
+    uint32_t n_prio_bits;
 
     /* If we present the GICv2 without security extensions to a guest,
      * the guest can configure the GICC_CTLR to configure group 1 binary point
-- 
2.7.4