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Re: [Xen-devel] [RFC PATCH 08/24] ARM: GICv3: introduce separate pending_irq structs for LPIs



Hi Andre,

On 28/09/16 19:24, Andre Przywara wrote:
+/*
+ * Holding struct pending_irq's for each possible virtual LPI in each domain
+ * requires too much Xen memory, also a malicious guest could potentially
+ * spam Xen with LPI map requests. We cannot cover those with (guest allocated)
+ * ITS memory, so we use a dynamic scheme of allocating struct pending_irq's
+ * on demand.
+ */
+struct pending_irq *lpi_to_pending(struct vcpu *v, unsigned int lpi,
+                                   bool allocate)
+{
+    struct lpi_pending_irq *lpi_irq, *empty = NULL;
+
+    /* TODO: locking! */
+    list_for_each_entry(lpi_irq, &v->arch.vgic.pending_lpi_list, entry)
+    {
+        if ( lpi_irq->pirq.irq == lpi )
+            return &lpi_irq->pirq;
+
+        if ( lpi_irq->pirq.irq == 0 && !empty )
+            empty = lpi_irq;
+    }
+
+    if ( !allocate )
+        return NULL;
+
+    if ( !empty )
+    {
+        empty = xzalloc(struct lpi_pending_irq);

xzalloc can return NULL if we fail to allocate memory.

+        vgic_init_pending_irq(&empty->pirq, lpi);
+        list_add_tail(&empty->entry, &v->arch.vgic.pending_lpi_list);
+    } else
+    {
+        empty->pirq.status = 0;
+        empty->pirq.irq = lpi;
+    }
+
+    return &empty->pirq;
+}
+

Regards,

--
Julien Grall

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