[Xen-devel] [PATCH V2] xen/arm: Missing +1 when then number of interrupt lines for the GIC is computed

[Julien Grall <julien.grall@xxxxxxxxxx>]

In the GIC manual, the number of interrupt lines is computed with the following
formula: 32(N + 1) where N is the value retrieved from GICD_TYPER.

Without the +1 Xen doesn't initialize the last 32 interrupts and can get
garbagge on these registers.

Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
---
 Modifications since v1:
   - Precise the impact in the commit message
   - Add description for the variable "lines"

 xen/arch/arm/gic.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 377b676..0fd8635 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -44,7 +44,7 @@ static struct {
     paddr_t cbase;       /* Address of CPU interface registers */
     paddr_t hbase;       /* Address of virtual interface registers */
     paddr_t vbase;       /* Address of virtual cpu interface registers */
-    unsigned int lines;
+    unsigned int lines;  /* Number of interrupts (SPIs + PPIs + SGIs) */
     unsigned int cpus;
     spinlock_t lock;
 } gic;
@@ -214,7 +214,7 @@ static int gic_route_irq(unsigned int irq, bool_t level,
 
     ASSERT(!(cpu_mask & ~0xff));  /* Targets bitmap only supports 8 CPUs */
     ASSERT(priority <= 0xff);     /* Only 8 bits of priority */
-    ASSERT(irq < gic.lines + 32); /* Can't route interrupts that don't exist */
+    ASSERT(irq < gic.lines);      /* Can't route interrupts that don't exist */
 
     spin_lock_irqsave(&desc->lock, flags);
     spin_lock(&gic.lock);
@@ -251,7 +251,7 @@ static void __init gic_dist_init(void)
     GICD[GICD_CTLR] = 0;
 
     type = GICD[GICD_TYPER];
-    gic.lines = 32 * (type & GICD_TYPE_LINES);
+    gic.lines = 32 * ((type & GICD_TYPE_LINES) + 1);
     gic.cpus = 1 + ((type & GICD_TYPE_CPUS) >> 5);
     printk("GIC: %d lines, %d cpu%s%s (IID %8.8x).\n",
            gic.lines, gic.cpus, (gic.cpus == 1) ? "" : "s",
-- 
1.7.10.4


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