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Re: [Xen-devel] [PATCH-4.5 4/4] xen/arm: set GICH_HCR_NPIE if all the LRs are in use





On 07/02/14 18:56, Stefano Stabellini wrote:
On return to guest, if there are no free LRs and we still have more
interrupt to inject, set GICH_HCR_NPIE so that we are going to receive a
maintenance interrupt when no pending interrupts are present in the LR
registers.
The maintenance interrupt handler won't do anything anymore, but
receiving the interrupt is going to cause gic_inject to be called on
return to guest that is going to clear the old LRs and inject new
interrupts.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
  xen/arch/arm/gic.c |    8 +++++++-
  1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 87bd5d3..bee2618 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -810,8 +810,14 @@ void gic_inject(void)
      gic_restore_pending_irqs(current);
      if (!gic_events_need_delivery())
          gic_inject_irq_stop();
-    else
+    else {
          gic_inject_irq_start();
+    }
+
+    if ( !list_empty(&current->arch.vgic.lr_pending) )
+        GICH[GICH_HCR] = GICH_HCR_EN | GICH_HCR_NPIE;
+    else
+        GICH[GICH_HCR] = GICH_HCR_EN;

Any reason to not move this in the else?

BTW, I think we can safely avoid to reinject the IRQ for the event channels if there is pending events. It will also avoid spurious IRQ on some specific case :).

--
Julien Grall

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