xen/arm: allow dynamically assigned SGI handlers

Updates so request_irq() can be used with a dynamically assigned SGI irq
as input. This prepares for a later patch where an FF-A schedule
receiver interrupt handler is installed for an SGI generated by the
secure world.

>From the Arm Base System Architecture v1.0C [1]:
"The system shall implement at least eight Non-secure SGIs, assigned to
interrupt IDs 0-7."

gic_route_irq_to_xen() don't gic_set_irq_type() for SGIs since they are
always edge triggered.

gic_interrupt() is updated to route the dynamically assigned SGIs to
do_IRQ() instead of do_sgi(). The latter still handles the statically
assigned SGI handlers like for instance GIC_SGI_CALL_FUNCTION.

[1] https://developer.arm.com/documentation/den0094/

Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
Acked-by: Julien Grall <jgrall@amazon.com>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>

xen/arch/arm/gic.c

@@ -38,7 +38,7 @@ 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);
+    BUILD_BUG_ON(GIC_SGI_STATIC_MAX > NR_GIC_SGI);
 }
 
 void register_gic_ops(const struct gic_hw_operations *ops)
@@ -117,7 +117,9 @@ void gic_route_irq_to_xen(struct irq_desc *desc, unsigned int priority)
 
     desc->handler = gic_hw_ops->gic_host_irq_type;
 
-    gic_set_irq_type(desc, desc->arch.type);
+    /* SGIs are always edge-triggered, so there is need to set it */
+    if ( desc->irq >= NR_GIC_SGI)
+        gic_set_irq_type(desc, desc->arch.type);
     gic_set_irq_priority(desc, priority);
 }
 
@@ -322,7 +324,7 @@ void gic_disable_cpu(void)
     gic_hw_ops->disable_interface();
 }
 
-static void do_sgi(struct cpu_user_regs *regs, enum gic_sgi sgi)
+static void do_static_sgi(struct cpu_user_regs *regs, enum gic_sgi sgi)
 {
     struct irq_desc *desc = irq_to_desc(sgi);
 
@@ -367,7 +369,7 @@ void gic_interrupt(struct cpu_user_regs *regs, int is_fiq)
         /* Reading IRQ will ACK it */
         irq = gic_hw_ops->read_irq();
 
-        if ( likely(irq >= 16 && irq < 1020) )
+        if ( likely(irq >= GIC_SGI_STATIC_MAX && irq < 1020) )
         {
             isb();
             do_IRQ(regs, irq, is_fiq);
@@ -379,7 +381,7 @@ void gic_interrupt(struct cpu_user_regs *regs, int is_fiq)
         }
         else if ( unlikely(irq < 16) )
         {
-            do_sgi(regs, irq);
+            do_static_sgi(regs, irq);
         }
         else
         {

xen/arch/arm/include/asm/gic.h

@@ -285,7 +285,7 @@ enum gic_sgi {
     GIC_SGI_EVENT_CHECK,
     GIC_SGI_DUMP_STATE,
     GIC_SGI_CALL_FUNCTION,
-    GIC_SGI_MAX,
+    GIC_SGI_STATIC_MAX,
 };
 
 /* SGI irq mode types */

xen/arch/arm/irq.c

@@ -142,7 +142,13 @@ void __init init_IRQ(void)
 
     spin_lock(&local_irqs_type_lock);
     for ( irq = 0; irq < NR_LOCAL_IRQS; irq++ )
-        local_irqs_type[irq] = IRQ_TYPE_INVALID;
+    {
+        /* SGIs are always edge-triggered */
+        if ( irq < NR_GIC_SGI )
+            local_irqs_type[irq] = IRQ_TYPE_EDGE_RISING;
+        else
+            local_irqs_type[irq] = IRQ_TYPE_INVALID;
+    }
     spin_unlock(&local_irqs_type_lock);
 
     BUG_ON(init_local_irq_data(smp_processor_id()) < 0);
@@ -214,9 +220,12 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int is_fiq)
 
     perfc_incr(irqs);
 
-    ASSERT(irq >= 16); /* SGIs do not come down this path */
+    /* Statically assigned SGIs do not come down this path */
+    ASSERT(irq >= GIC_SGI_STATIC_MAX);
 
-    if ( irq < 32 )
+    if ( irq < NR_GIC_SGI )
+        perfc_incr(ipis);
+    else if ( irq < NR_GIC_LOCAL_IRQS )
         perfc_incr(ppis);
     else
         perfc_incr(spis);
@@ -250,6 +259,7 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int is_fiq)
          * The irq cannot be a PPI, we only support delivery of SPIs to
          * guests.
          */
+        ASSERT(irq >= NR_GIC_SGI);
         vgic_inject_irq(info->d, NULL, info->virq, true);
         goto out_no_end;
     }
@@ -386,7 +396,7 @@ int setup_irq(unsigned int irq, unsigned int irqflags, struct irqaction *new)
     {
         gic_route_irq_to_xen(desc, GIC_PRI_IRQ);
         /* It's fine to use smp_processor_id() because:
-         * For PPI: irq_desc is banked
+         * For SGI and PPI: irq_desc is banked
          * For SPI: we don't care for now which CPU will receive the
          * interrupt
          * TODO: Handle case where SPI is setup on different CPU than