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Re: [Xen-devel] [RFC PATCH v2 03/22] ARM: vGIC: move gic_raise_inflight_irq() into vgic_vcpu_inject_irq()

Hi Andre,

On 21/07/17 20:59, Andre Przywara wrote:
Currently there is a gic_raise_inflight_irq(), which serves the very
special purpose of handling a newly injected interrupt while an older
one is still handled. This has only one user, in vgic_vcpu_inject_irq().

Now with the introduction of the pending_irq lock this will later on
result in a nasty deadlock, which can only be solved properly by
actually embedding the function into the caller (and dropping the lock
later in-between).

This has the admittedly hideous consequence of needing to export
gic_update_one_lr(), but this will go away in a later stage of a rework.
In this respect this patch is more a temporary kludge.

Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
 xen/arch/arm/gic.c        | 30 +-----------------------------
 xen/arch/arm/vgic.c       | 11 ++++++++++-
 xen/include/asm-arm/gic.h |  2 +-
 3 files changed, 12 insertions(+), 31 deletions(-)

diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 2c99d71..5bd66a2 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -44,8 +44,6 @@ static DEFINE_PER_CPU(uint64_t, lr_mask);

 #undef GIC_DEBUG

-static void gic_update_one_lr(struct vcpu *v, int i);
 static const struct gic_hw_operations *gic_hw_ops;

 void register_gic_ops(const struct gic_hw_operations *ops)
@@ -416,32 +414,6 @@ void gic_remove_irq_from_queues(struct vcpu *v, struct 
pending_irq *p)
     gic_remove_from_lr_pending(v, p);

-void gic_raise_inflight_irq(struct vcpu *v, unsigned int virtual_irq)
-    struct pending_irq *n = irq_to_pending(v, virtual_irq);
-    /* If an LPI has been removed meanwhile, there is nothing left to raise. */
-    if ( unlikely(!n) )
-        return;
-    ASSERT(spin_is_locked(&v->arch.vgic.lock));
-    /* Don't try to update the LR if the interrupt is disabled */
-    if ( !test_bit(GIC_IRQ_GUEST_ENABLED, &n->status) )
-        return;
-    if ( list_empty(&n->lr_queue) )
-    {
-        if ( v == current )
-            gic_update_one_lr(v, n->lr);
-    }
-#ifdef GIC_DEBUG
-    else
-        gdprintk(XENLOG_DEBUG, "trying to inject irq=%u into d%dv%d, when it is 
still lr_pending\n",
-                 virtual_irq, v->domain->domain_id, v->vcpu_id);
  * Find an unused LR to insert an IRQ into, starting with the LR given
  * by @lr. If this new interrupt is a PRISTINE LPI, scan the other LRs to
@@ -503,7 +475,7 @@ void gic_raise_guest_irq(struct vcpu *v, unsigned int 
     gic_add_to_lr_pending(v, p);

-static void gic_update_one_lr(struct vcpu *v, int i)
+void gic_update_one_lr(struct vcpu *v, int i)
     struct pending_irq *p;
     int irq;
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 38dacd3..7b122cd 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -536,7 +536,16 @@ void vgic_vcpu_inject_irq(struct vcpu *v, unsigned int 

     if ( !list_empty(&n->inflight) )
-        gic_raise_inflight_irq(v, virq);
+        bool update = test_bit(GIC_IRQ_GUEST_ENABLED, &n->status) &&
+                      list_empty(&n->lr_queue) && (v == current);
+        if ( update )
+            gic_update_one_lr(v, n->lr);
+#ifdef GIC_DEBUG
+        else
+            gdprintk(XENLOG_DEBUG, "trying to inject irq=%u into d%dv%d, when it is 
still lr_pending\n",
+                     n->irq, v->domain->domain_id, v->vcpu_id);

The previous code was only printing this message when the pending_irq is queued. Now you will print any time you don't update the LR.

         goto out;

diff --git a/xen/include/asm-arm/gic.h b/xen/include/asm-arm/gic.h
index 6203dc5..cf8b8fb 100644
--- a/xen/include/asm-arm/gic.h
+++ b/xen/include/asm-arm/gic.h
@@ -237,12 +237,12 @@ int gic_remove_irq_from_guest(struct domain *d, unsigned 
int virq,

 extern void gic_inject(void);
 extern void gic_clear_pending_irqs(struct vcpu *v);
+extern void gic_update_one_lr(struct vcpu *v, int lr);
 extern int gic_events_need_delivery(void);

 extern void init_maintenance_interrupt(void);
 extern void gic_raise_guest_irq(struct vcpu *v, unsigned int irq,
         unsigned int priority);
-extern void gic_raise_inflight_irq(struct vcpu *v, unsigned int virtual_irq);
 extern void gic_remove_from_lr_pending(struct vcpu *v, struct pending_irq *p);
 extern void gic_remove_irq_from_queues(struct vcpu *v, struct pending_irq *p);


Julien Grall

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