[Xen-devel] [PATCH] Dont' round-robin the callback interrupt

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

# HG changeset patch
# User Paul Durrant <paul.durrant@xxxxxxxxxx>
# Date 1278949925 -3600
# Node ID 0f3d7e651362dfe76a98c248d0f71795f624ed78
# Parent  f12837d7a50e3e5f843bd1a7113bb329661c7dd0
Dont' round-robin the callback interrupt.

Arrange that the event channel callback interrupt always goes to the
lowest vcpu with a matching local apic. This should, in most cases,
be VCPU0 (to which all event channels are bound for HVM guests) but
this cannot be guaranteed.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
CC: Tim Deegan <tim.deegan@xxxxxxxxxx>

diff -r f12837d7a50e -r 0f3d7e651362 xen/arch/x86/hvm/vioapic.c
--- a/xen/arch/x86/hvm/vioapic.c        Mon Jul 12 10:48:34 2010 +0100
+++ b/xen/arch/x86/hvm/vioapic.c        Mon Jul 12 16:52:05 2010 +0100
@@ -276,6 +276,29 @@
     return pt_active(&pit->pt0);
 }
 
+static int is_callback_via(struct domain *d, int irq)
+{
+    struct hvm_irq *hvm_irq = &d->arch.hvm_domain.irq;
+
+    switch ( hvm_irq->callback_via_type )
+    {
+    case HVMIRQ_callback_gsi: {
+        unsigned int gsi = hvm_irq->callback_via.gsi;
+
+        return irq == gsi;
+    }
+    case HVMIRQ_callback_pci_intx: {
+        unsigned int pdev  = hvm_irq->callback_via.pci.dev;
+        unsigned int pintx = hvm_irq->callback_via.pci.intx;
+
+        return irq == hvm_pci_intx_gsi(pdev, pintx);
+    }
+    case HVMIRQ_callback_vector:
+    default:
+        return 0;
+    }
+}
+
 static void vioapic_deliver(struct hvm_hw_vioapic *vioapic, int irq)
 {
     uint16_t dest = vioapic->redirtbl[irq].fields.dest_id;
@@ -307,7 +330,11 @@
         }
         else
 #endif
+        if ( is_callback_via(d, irq) )
+            target = vlapic_lowest_vcpu(d, NULL, 0, dest, dest_mode);
+        else
             target = vlapic_lowest_prio(d, NULL, 0, dest, dest_mode);
+
         if ( target != NULL )
         {
             ioapic_inj_irq(vioapic, target, vector, trig_mode, delivery_mode);
diff -r f12837d7a50e -r 0f3d7e651362 xen/arch/x86/hvm/vlapic.c
--- a/xen/arch/x86/hvm/vlapic.c Mon Jul 12 10:48:34 2010 +0100
+++ b/xen/arch/x86/hvm/vlapic.c Mon Jul 12 16:52:05 2010 +0100
@@ -354,6 +354,28 @@
     if ( target != NULL )
         d->arch.hvm_domain.irq.round_robin_prev_vcpu =
             vlapic_vcpu(target)->vcpu_id;
+
+    return target;
+}
+
+struct vlapic *vlapic_lowest_vcpu(
+    struct domain *d, struct vlapic *source,
+    int short_hand, uint8_t dest, uint8_t dest_mode)
+{
+    struct vlapic *vlapic, *target = NULL;
+    struct vcpu *v;
+
+    if ( unlikely(!d->vcpu) )
+        return NULL;
+
+    for ( v = d->vcpu[0]; v; v = v->next_in_list ) {
+        vlapic = vcpu_vlapic(v);
+        if ( vlapic_match_dest(vlapic, source, short_hand, dest, dest_mode) &&
+             vlapic_enabled(vlapic) ) {
+            target = vlapic;
+            break;
+        }
+    }
 
     return target;
 }
diff -r f12837d7a50e -r 0f3d7e651362 xen/include/asm-x86/hvm/vlapic.h
--- a/xen/include/asm-x86/hvm/vlapic.h  Mon Jul 12 10:48:34 2010 +0100
+++ b/xen/include/asm-x86/hvm/vlapic.h  Mon Jul 12 16:52:05 2010 +0100
@@ -100,6 +100,10 @@
     struct domain *d, struct vlapic *source,
     int short_hand, uint8_t dest, uint8_t dest_mode);
 
+struct vlapic *vlapic_lowest_vcpu(
+    struct domain *d, struct vlapic *source,
+    int short_hand, uint8_t dest, uint8_t dest_mode);
+
 bool_t vlapic_match_dest(
     struct vlapic *target, struct vlapic *source,
     int short_hand, uint8_t dest, uint8_t dest_mode);

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