[PATCH v3] xen/dom0less: support for vcpu affinity

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

Add vcpu affinity to the dom0less bindings. Example:

    dom1 {
            ...
            cpus = <4>;
            vcpu0 {
                   compatible = "xen,vcpu-affinity";
                   id = <0>;
                   hard-affinity = "4-7";
            };
            vcpu1 {
                   compatible = "xen,vcpu-affinity";
                   id = <1>;
                   hard-affinity = "0-3";
            };
            vcpu2 {
                   compatible = "xen,vcpu-affinity";
                   id = <2>;
                   hard-affinity = "1,6";
            };
            ...

Note that the property hard-affinity is optional. It is possible to add
other properties in the future not only to specify soft affinity, but
also to provide more precise methods for configuring affinity. For
instance, on ARM the MPIDR could be use to specify the pCPU. For now, it
is left to the future.

Signed-off-by: Xenia Ragiadakou <xenia.ragiadakou@xxxxxxx>
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
---
Changes in v3:
- improve commit message
- improve binding doc
- add panic on invalid pCPU
- move parsing to a separate function

diff --git a/docs/misc/arm/device-tree/booting.txt 
b/docs/misc/arm/device-tree/booting.txt
index 9c881baccc..10e55c825c 100644
--- a/docs/misc/arm/device-tree/booting.txt
+++ b/docs/misc/arm/device-tree/booting.txt
@@ -324,6 +324,27 @@ The ramdisk sub-node has the following properties:
     property because it will be created by the UEFI stub on boot.
     This option is needed only when UEFI boot is used.
 
+Under the "xen,domain" compatible node, it is possible optionally to add
+one or more sub-nodes to configure vCPU affinity. The vCPU affinity
+sub-node has the following properties:
+
+- compatible
+
+    "xen,vcpu-affinity"
+
+- id
+
+    A 32-bit integer that specifies the vCPU id. 0 is the first vCPU.
+    The last vCPU is cpus-1, where "cpus" is the number of vCPUs
+    specified with the "cpus" property under the "xen,domain" node.
+
+- hard-affinity
+
+    Optional. A string specifying the hard affinity configuration for the
+    vCPU: a comma-separated list of pCPUs or ranges of pCPUs is used.
+    Ranges are hyphen-separated intervals (such as `0-4`) and are inclusive
+    on both sides. The numbers refer to pCPU ids.
+
 
 Example
 =======
diff --git a/xen/arch/arm/dom0less-build.c b/xen/arch/arm/dom0less-build.c
index 49d1f14d65..e364820189 100644
--- a/xen/arch/arm/dom0less-build.c
+++ b/xen/arch/arm/dom0less-build.c
@@ -810,6 +810,68 @@ static int __init construct_domU(struct domain *d,
     return rc;
 }
 
+static void __init domain_vcpu_affinity(struct domain *d,
+                                        const struct dt_device_node *node)
+{
+    const char *hard_affinity_str = NULL;
+    struct dt_device_node *np;
+    uint32_t val;
+    int rc;
+
+    dt_for_each_child_node(node, np)
+    {
+        const char *s;
+        struct vcpu *v;
+        cpumask_t affinity;
+
+        if ( !dt_device_is_compatible(np, "xen,vcpu-affinity") )
+            continue;
+
+        if ( !dt_property_read_u32(np, "id", &val) )
+            continue;
+
+        if ( val >= d->max_vcpus )
+            panic("Invalid vcpu_id %u for domain %s\n", val, 
dt_node_name(node));
+
+        v = d->vcpu[val];
+        rc = dt_property_read_string(np, "hard-affinity", &hard_affinity_str);
+        if ( rc < 0 )
+            continue;
+
+        s = hard_affinity_str;
+        cpumask_clear(&affinity);
+        while ( *s != '\0' )
+        {
+            unsigned int start, end;
+
+            start = simple_strtoul(s, &s, 0);
+
+            if ( *s == '-' )    /* Range */
+            {
+                s++;
+                end = simple_strtoul(s, &s, 0);
+            }
+            else                /* Single value */
+                end = start;
+
+            if ( end >= nr_cpu_ids )
+                panic("Invalid pCPU %u for domain %s\n", end, 
dt_node_name(node));
+
+            for ( ; start <= end; start++ )
+                cpumask_set_cpu(start, &affinity);
+
+            if ( *s == ',' )
+                s++;
+            else if ( *s != '\0' )
+                break;
+        }
+
+        rc = vcpu_set_hard_affinity(v, &affinity);
+        if ( rc )
+            panic("vcpu%d: failed to set hard affinity\n", v->vcpu_id);
+    }
+}
+
 void __init create_domUs(void)
 {
     struct dt_device_node *node;
@@ -992,6 +1054,8 @@ void __init create_domUs(void)
         if ( rc )
             panic("Could not set up domain %s (rc = %d)\n",
                   dt_node_name(node), rc);
+
+        domain_vcpu_affinity(d, node);
     }
 }