xen/arm: irq: Don't use _IRQ_PENDING when handling host interrupt

While SPIs are shared between CPU, it is not possible to receive the
same interrupts on a different CPU while the interrupt is in active
state.

For host interrupt (i.e routed to Xen), the deactivation of the
interrupt is done at the end of the handling. This can alternatively be
done outside of the handler by calling gic_set_active_state().

At the moment, gic_set_active_state() is only called by the vGIC for
interrupt routed to the guest. It is hard to find a reason for Xen to
directly play with the active state for interrupt routed to Xen.

To simplify the handling of host interrupt, gic_set_activate_state() is
now restricted to interrupts routed to guest.

This means the _IRQ_PENDING logic is now unecessary on Arm as a same
interrupt can never come up while in the loop and nobody should play
with the flag behind our back.

[Stefano: improve in-code comment]

Signed-off-by: Julien Grall <julien.grall@arm.com>
Signed-off-by: Stefano Stabellini <stefanos@xilinx.com>
Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index c51cf333cee7d62288f396c83ca74797a4f394bc..3877657a5277975a38881762288090b91a1efe44 100644 (file)
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -199,6 +199,7 @@ int request_irq(unsigned int irq, unsigned int irqflags,
 void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int is_fiq)
 {
     struct irq_desc *desc = irq_to_desc(irq);
+    struct irqaction *action;
 
     perfc_incr(irqs);
 
@@ -242,35 +243,22 @@ void do_IRQ(struct cpu_user_regs *regs, unsigned int irq, int is_fiq)
         goto out_no_end;
     }
 
-    set_bit(_IRQ_PENDING, &desc->status);
-
-    /*
-     * Since we set PENDING, if another processor is handling a different
-     * instance of this same irq, the other processor will take care of it.
-     */
-    if ( test_bit(_IRQ_DISABLED, &desc->status) ||
-         test_bit(_IRQ_INPROGRESS, &desc->status) )
+    if ( test_bit(_IRQ_DISABLED, &desc->status) )
         goto out;
 
     set_bit(_IRQ_INPROGRESS, &desc->status);
 
-    while ( test_bit(_IRQ_PENDING, &desc->status) )
-    {
-        struct irqaction *action;
+    action = desc->action;
 
-        clear_bit(_IRQ_PENDING, &desc->status);
-        action = desc->action;
+    spin_unlock_irq(&desc->lock);
 
-        spin_unlock_irq(&desc->lock);
-
-        do
-        {
-            action->handler(irq, action->dev_id, regs);
-            action = action->next;
-        } while ( action );
+    do
+    {
+        action->handler(irq, action->dev_id, regs);
+        action = action->next;
+    } while ( action );
 
-        spin_lock_irq(&desc->lock);
-    }
+    spin_lock_irq(&desc->lock);
 
     clear_bit(_IRQ_INPROGRESS, &desc->status);
 

diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index fab02f19f76e8815dc3251a1522ee35a4bfb0689..793d324b337a9e01bfd0460132020e7a8bc93469 100644 (file)
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -400,9 +400,14 @@ static inline unsigned int gic_get_nr_lrs(void)
  * Set the active state of an IRQ. This should be used with care, as this
  * directly forces the active bit, without considering the GIC state machine.
  * For private IRQs this only works for those of the current CPU.
+ *
+ * This function should only be called for interrupts routed to the
+ * guest. The flow of interrupts routed to Xen is not able cope with
+ * software changes to the active state.
  */
 static inline void gic_set_active_state(struct irq_desc *irqd, bool state)
 {
+    ASSERT(test_bit(_IRQ_GUEST, &irqd->status));
     gic_hw_ops->set_active_state(irqd, state);
 }