[PATCH 16/21] xen/arm: Balance Dom0 vCPU assignment across NUMA nodes

[Hirokazu Takahashi <taka@xxxxxxxxxxxxx>]

Configure the assignment of Dom0 vCPUs to NUMA nodes, aiming to balance
the compute load across the available nodes.
---
 xen/arch/arm/domain_build.c | 46 +++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 1deb4c1139..a62adafa19 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -1225,6 +1225,34 @@ int __init make_psci_node(void *fdt)
     return res;
 }
 
+/*
+ * Map a Dom0 vCPU ID to a target NUMA node ID.
+ */
+static nodeid_t __init dom0_vcpu_to_node(const struct domain *d, unsigned int 
vcpu_id)
+{
+    nodeid_t nodes[MAX_NUMNODES];
+    unsigned int nr_nodes = 0;
+    unsigned int vcpus_per_node;
+    unsigned int node_idx;
+    nodeid_t n;
+
+    if ( nodes_empty(d->node_affinity) )
+        return 0;
+
+    for_each_node_mask(n, d->node_affinity)
+        nodes[nr_nodes++] = n;
+
+    if ( nr_nodes == 0 )
+        return 0;
+
+    vcpus_per_node = (d->max_vcpus + nr_nodes - 1) / nr_nodes;
+    node_idx = vcpu_id / vcpus_per_node;
+
+    ASSERT(node_idx < nr_nodes);
+
+    return nodes[node_idx];
+}
+
 int __init make_cpus_node(const struct domain *d, struct kernel_info *kinfo)
 {
     int res;
@@ -1907,6 +1935,24 @@ int __init construct_domain(struct domain *d, struct 
kernel_info *kinfo)
             vcpu_switch_to_aarch64_mode(d->vcpu[i]);
     }
 
+    /*
+     * If Dom0 has specific NUMA node affinity configured, bind each vCPU
+     * to its designated physical node.
+     */
+    for ( i = 0; i < d->max_vcpus; i++ )
+    {
+        struct vcpu *v = d->vcpu[i];
+        nodeid_t pnode;
+        const cpumask_t *nodemask;
+
+        if ( !v ) continue;
+
+        pnode = dom0_vcpu_to_node(d, i);
+        nodemask = &node_to_cpumask(pnode);
+
+        vcpu_set_hard_affinity(v, nodemask);
+    }
+
     domain_update_node_affinity(d);
 
     v->is_initialised = 1;
-- 
2.43.0