xen/18785-vlapic-lowest-prio.patch

# HG changeset patch
# User Keir Fraser <keir.fraser@citrix.com>
# Date 1227006996 0
# Node ID ae891977a4d3f5d8d8330ed3796881867b4d88a8
# Parent  2604400f75e318dc9f5201e3626213290a89862a
x86, hvm: Implement interrupt routing to least priority processor.
References: bnc#429904

Instead of round robin the vcpu with the lowest processor
priority is selected for the interrupt. If multiple vcpus
share the same low priority then interrupts are distributed between
those round robin.

Signed-off-by: Juergen Gross <juergen.gross@fujitsu-siemens.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>

--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -344,8 +344,8 @@ static void vioapic_deliver(struct hvm_h
         }
         else
 #endif
-            target = apic_round_robin(vioapic_domain(vioapic),
-                                      vector, deliver_bitmask);
+            target = apic_lowest_prio(vioapic_domain(vioapic),
+                                      deliver_bitmask);
         if ( target != NULL )
         {
             ioapic_inj_irq(vioapic, target, vector, trig_mode, delivery_mode);
--- a/xen/arch/x86/hvm/vlapic.c
+++ b/xen/arch/x86/hvm/vlapic.c
@@ -377,26 +377,30 @@ static int vlapic_accept_irq(struct vcpu
 }
 
 /* This function is used by both ioapic and lapic.The bitmap is for vcpu_id. */
-struct vlapic *apic_round_robin(
-    struct domain *d, uint8_t vector, uint32_t bitmap)
+struct vlapic *apic_lowest_prio(struct domain *d, uint32_t bitmap)
 {
-    int next, old;
-    struct vlapic *target = NULL;
+    int old = d->arch.hvm_domain.irq.round_robin_prev_vcpu;
+    uint32_t ppr, target_ppr = UINT_MAX;
+    struct vlapic *vlapic, *target = NULL;
+    struct vcpu *v;
 
-    old = next = d->arch.hvm_domain.irq.round_robin_prev_vcpu;
+    if ( unlikely((v = d->vcpu[old]) == NULL) )
+        return NULL;
 
     do {
-        if ( ++next == MAX_VIRT_CPUS ) 
-            next = 0;
-        if ( (d->vcpu[next] == NULL) || !test_bit(next, &bitmap) )
-            continue;
-        target = vcpu_vlapic(d->vcpu[next]);
-        if ( vlapic_enabled(target) )
-            break;
-        target = NULL;
-    } while ( next != old );
+        v = v->next_in_list ? : d->vcpu[0];
+        vlapic = vcpu_vlapic(v);
+        if ( test_bit(v->vcpu_id, &bitmap) && vlapic_enabled(vlapic) &&
+             ((ppr = vlapic_get_ppr(vlapic)) < target_ppr) )
+        {
+            target = vlapic;
+            target_ppr = ppr;
+        }
+    } while ( v->vcpu_id != old );
 
-    d->arch.hvm_domain.irq.round_robin_prev_vcpu = next;
+    if ( target != NULL )
+        d->arch.hvm_domain.irq.round_robin_prev_vcpu =
+            vlapic_vcpu(target)->vcpu_id;
 
     return target;
 }
@@ -456,7 +460,7 @@ static int vlapic_ipi(
 
     if ( delivery_mode == APIC_DM_LOWEST )
     {
-        target = apic_round_robin(vlapic_domain(v), vector, lpr_map);
+        target = apic_lowest_prio(vlapic_domain(v), lpr_map);
         if ( target != NULL )
             rc = vlapic_accept_irq(vlapic_vcpu(target), delivery_mode,
                                    vector, level, trig_mode);
--- a/xen/arch/x86/hvm/vmsi.c
+++ b/xen/arch/x86/hvm/vmsi.c
@@ -152,7 +152,7 @@ int vmsi_deliver(struct domain *d, int p
     {
     case dest_LowestPrio:
     {
-        target = apic_round_robin(d, vector, deliver_bitmask);
+        target = apic_lowest_prio(d, deliver_bitmask);
         if ( target != NULL )
             vmsi_inj_irq(d, target, vector, trig_mode, delivery_mode);
         else
--- a/xen/include/asm-x86/hvm/vlapic.h
+++ b/xen/include/asm-x86/hvm/vlapic.h
@@ -93,8 +93,7 @@ void vlapic_msr_set(struct vlapic *vlapi
 
 int vlapic_accept_pic_intr(struct vcpu *v);
 
-struct vlapic *apic_round_robin(
-    struct domain *d, uint8_t vector, uint32_t bitmap);
+struct vlapic *apic_lowest_prio(struct domain *d, uint32_t bitmap);
 
 int vlapic_match_logical_addr(struct vlapic *vlapic, uint8_t mda);