[Xen-devel] [PATCH 25/57] ARM: evtchn: Handle level triggered IRQs correctly

[Andre Przywara <andre.przywara@xxxxxxxxxx>]

The event channel IRQ has level triggered semantics, however the current
VGIC treats everything as edge triggered.
To correctly process those IRQs, we have to lower the (virtual) IRQ line
at some point in time, depending on whether ther interrupt condition
still prevails.
Check the per-VCPU evtchn_upcall_pending variable to make the interrupt
line match its status, and call this function upon every hypervisor
entry.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
---
Changelog RFC ... v1:
- no changes

 xen/arch/arm/domain.c       | 7 +++++++
 xen/arch/arm/traps.c        | 1 +
 xen/include/asm-arm/event.h | 1 +
 3 files changed, 9 insertions(+)

diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index a7bba3ad44..11a46aa27f 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -955,6 +955,13 @@ void vcpu_mark_events_pending(struct vcpu *v)
     vgic_inject_irq(v->domain, v, v->domain->arch.evtchn_irq, true);
 }
 
+void vcpu_update_evtchn_irq(struct vcpu *v)
+{
+    bool pending = vcpu_info(v, evtchn_upcall_pending);
+
+    vgic_inject_irq(v->domain, v, v->domain->arch.evtchn_irq, pending);
+}
+
 /* The ARM spec declares that even if local irqs are masked in
  * the CPSR register, an irq should wake up a cpu from WFI anyway.
  * For this reason we need to check for irqs that need delivery,
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 0713723bb7..fcf5db50ae 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2029,6 +2029,7 @@ static void enter_hypervisor_head(struct cpu_user_regs 
*regs)
          * triggered interrupts before syncing back the VGIC state.
          */
         vtimer_sync(current);
+        vcpu_update_evtchn_irq(current);
 
         vgic_sync_from_lrs(current);
     }
diff --git a/xen/include/asm-arm/event.h b/xen/include/asm-arm/event.h
index c4c79fa87d..eafb2e7f3e 100644
--- a/xen/include/asm-arm/event.h
+++ b/xen/include/asm-arm/event.h
@@ -6,6 +6,7 @@
 
 void vcpu_kick(struct vcpu *v);
 void vcpu_mark_events_pending(struct vcpu *v);
+void vcpu_update_evtchn_irq(struct vcpu *v);
 void vcpu_block_unless_event_pending(struct vcpu *v);
 
 static inline int vcpu_event_delivery_is_enabled(struct vcpu *v)
-- 
2.14.1


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