[Xen-devel] [RFC PATCH 18/49] 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>
---
 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 e76cfdfe83..87bd493924 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 2d770a14a5..f57ef2141a 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -2025,6 +2025,7 @@ static void enter_hypervisor_head(struct cpu_user_regs 
*regs)
             current->arch.hcr_el2 = READ_SYSREG(HCR_EL2);
 
         vtimer_sync(current);
+        vcpu_update_evtchn_irq(current);
         gic_clear_lrs(current);
     }
 }
diff --git a/xen/include/asm-arm/event.h b/xen/include/asm-arm/event.h
index e8c2a6cb44..87ef76e3d5 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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