xen/arm: gic: Remove pointless assertion against enum gic_sgi

The Arm Compiler will complain that the assertions ASSERT(sgi < 16) are
always true. This is because sgi is an item of the enum gic_sgi and
should always contain less than 16 SGIs.

Rather than using ASSERTs, introduce a new item in the enum that could
be checked against a build time.

Take the opportunity to remove the specific assigned values for each
item. This is fine because enum always starts at zero and values will be
assigned by increment of one. None of our code also rely on hardcoded
value.

[stefano: grammar fixes in commit message]

Signed-off-by: Julien Grall <julien@xen.org>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
CC: Andrii Anisov <andrii_anisov@epam.com>

xen/arch/arm/gic.c

@@ -44,6 +44,12 @@ DEFINE_PER_CPU(uint64_t, lr_mask);
 
 const struct gic_hw_operations *gic_hw_ops;
 
+static void __init __maybe_unused build_assertions(void)
+{
+    /* Check our enum gic_sgi only covers SGIs */
+    BUILD_BUG_ON(GIC_SGI_MAX > NR_GIC_SGI);
+}
+
 void register_gic_ops(const struct gic_hw_operations *ops)
 {
     gic_hw_ops = ops;
@@ -294,8 +300,6 @@ void __init gic_init(void)
 
 void send_SGI_mask(const cpumask_t *cpumask, enum gic_sgi sgi)
 {
-    ASSERT(sgi < 16); /* There are only 16 SGIs */
-
     gic_hw_ops->send_SGI(sgi, SGI_TARGET_LIST, cpumask);
 }
 
@@ -306,15 +310,11 @@ void send_SGI_one(unsigned int cpu, enum gic_sgi sgi)
 
 void send_SGI_self(enum gic_sgi sgi)
 {
-    ASSERT(sgi < 16); /* There are only 16 SGIs */
-
     gic_hw_ops->send_SGI(sgi, SGI_TARGET_SELF, NULL);
 }
 
 void send_SGI_allbutself(enum gic_sgi sgi)
 {
-   ASSERT(sgi < 16); /* There are only 16 SGIs */
-
    gic_hw_ops->send_SGI(sgi, SGI_TARGET_OTHERS, NULL);
 }
 

xen/include/asm-arm/gic.h

@@ -277,9 +277,10 @@ extern void gic_restore_state(struct vcpu *v);
 
 /* SGI (AKA IPIs) */
 enum gic_sgi {
-    GIC_SGI_EVENT_CHECK = 0,
-    GIC_SGI_DUMP_STATE  = 1,
-    GIC_SGI_CALL_FUNCTION = 2,
+    GIC_SGI_EVENT_CHECK,
+    GIC_SGI_DUMP_STATE,
+    GIC_SGI_CALL_FUNCTION,
+    GIC_SGI_MAX,
 };
 
 /* SGI irq mode types */