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Re: [Xen-devel] [RFC PATCH 24/49] ARM: new VGIC: Add IRQ sync/flush framework



Hi Andre,

On 09/02/18 14:39, Andre Przywara wrote:
+/* Requires the VCPU's ap_list_lock to be held. */
+static void vgic_flush_lr_state(struct vcpu *vcpu)
+{
+    struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
+    struct vgic_irq *irq;
+    int count = 0;
+
+    ASSERT(spin_is_locked(&vgic_cpu->ap_list_lock));
+
+    if ( compute_ap_list_depth(vcpu) > gic_get_nr_lrs() )
+        vgic_sort_ap_list(vcpu);
+
+    list_for_each_entry( irq, &vgic_cpu->ap_list_head, ap_list )
+    {
+        spin_lock(&irq->irq_lock);
+
+        if ( unlikely(vgic_target_oracle(irq) != vcpu) )
+            goto next;
+
+        /*
+         * If we get an SGI with multiple sources, try to get
+         * them in all at once.
+         */
+        do
+        {
+            vgic_populate_lr(vcpu, irq, count++);
+        } while ( irq->source && count < gic_get_nr_lrs() );
+
+next:
+        spin_unlock(&irq->irq_lock);
+
+        if ( count == gic_get_nr_lrs() )
+        {
+            if ( !list_is_last(&irq->ap_list, &vgic_cpu->ap_list_head) )
+                vgic_set_underflow(vcpu);
+            break;
+        }
+    }
+
+    vcpu->arch.vgic_cpu.used_lrs = count;
+
+    /* Nuke remaining LRs */
+    for ( ; count < gic_get_nr_lrs(); count++)
+        vgic_clear_lr(vcpu, count);

Why do you need to nuke the LRs here, don't you always zero them when clearing it?

Cheers,

--
Julien Grall

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