[PATCH v1 4/4] libxl: set vcpu affinity during domain creation

[Olaf Hering]

Since Xen 4.5 libxl allows to set affinities during domain creation.
This enables Xen to allocate the domain memory on NUMA systems close to
the specified pcpus.

Libvirt can now handle <domain/cputune/vcpupin> in domU.xml correctly.

Without this change, Xen will create the domU and assign NUMA memory and
vcpu affinities on its own. Later libvirt will adjust the affinity,
which may move the vcpus away from the assigned NUMA node.

Signed-off-by: Olaf Hering <olaf at aepfle.de>
---
 src/libxl/libxl_conf.c | 53 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/src/libxl/libxl_conf.c b/src/libxl/libxl_conf.c
index 3ccb00ec35..3a969c38cd 100644
--- a/src/libxl/libxl_conf.c
+++ b/src/libxl/libxl_conf.c
@@ -283,6 +283,56 @@ libxlMakeChrdevStr(virDomainChrDef *def, char **buf)
     return 0;
 }
 
+static int
+libxlDomainSetVcpuAffinities(virDomainDef *def,
+                             libxl_ctx *ctx,
+                             libxl_domain_build_info *b_info)
+{
+    libxl_bitmap *vcpu_affinity_array;
+    unsigned int vcpuid;
+    unsigned int vcpu_idx = 0;
+    virDomainVcpuDef *vcpu;
+    bool has_vcpu_pin = false;
+
+    /* Get highest vcpuid with cpumask */
+    for (vcpuid = 0; vcpuid < b_info->max_vcpus; vcpuid++) {
+        vcpu = virDomainDefGetVcpu(def, vcpuid);
+        if (!vcpu)
+            continue;
+        if (!vcpu->cpumask)
+            continue;
+        vcpu_idx = vcpuid;
+        has_vcpu_pin = true;
+    }
+    /* Nothing to do */
+    if (!has_vcpu_pin)
+        return 0;
+
+    /* Adjust index */
+    vcpu_idx++;
+
+    b_info->num_vcpu_hard_affinity = vcpu_idx;
+    /* Will be released by libxl_domain_config_dispose */
+    b_info->vcpu_hard_affinity = calloc(vcpu_idx, sizeof(libxl_bitmap));
+    vcpu_affinity_array = b_info->vcpu_hard_affinity;
+
+    for (vcpuid = 0; vcpuid < vcpu_idx; vcpuid++) {
+        libxl_bitmap *map = &vcpu_affinity_array[vcpuid];
+        libxl_bitmap_init(map);
+        /* libxl owns the bitmap */
+        if (libxl_cpu_bitmap_alloc(ctx, map, 0))
+            return -1;
+        vcpu = virDomainDefGetVcpu(def, vcpuid);
+        /* Apply the given mask, or allow unhandled vcpus to run anywhere */
+        if (vcpu && vcpu->cpumask)
+            virBitmapToDataBuf(vcpu->cpumask, map->map, map->size);
+        else
+            libxl_bitmap_set_any(map);
+    }
+    libxl_defbool_set(&b_info->numa_placement, false);
+    return 0;
+}
+
 static int
 libxlMakeDomBuildInfo(virDomainDef *def,
                       libxlDriverConfig *cfg,
@@ -320,6 +370,9 @@ libxlMakeDomBuildInfo(virDomainDef *def,
     for (i = 0; i < virDomainDefGetVcpus(def); i++)
         libxl_bitmap_set((&b_info->avail_vcpus), i);
 
+    if (libxlDomainSetVcpuAffinities(def, ctx, b_info))
+        return -1;
+
     switch ((virDomainClockOffsetType) clock.offset) {
     case VIR_DOMAIN_CLOCK_OFFSET_VARIABLE:
         if (clock.data.variable.basis == VIR_DOMAIN_CLOCK_BASIS_LOCALTIME)