[libvirt] [PATCH 3/7] conf: Initialize the pinning policy for vcpus

[Osier Yang]

Document for <vcpu>'s "cpuset" says:

Since 0.4.4, this element can contain an optional cpuset attribute,
which is a comma-separated list of physical CPU numbers that virtual
CPUs can be pinned to.

However, it's not the truth, libvirt actually pins the domain
process to the specified pCPUs by "cpuset" of <vcpu>. And the
vcpu thread are pinned to all available pCPUs if no <vcpupin>
is specified for it.

PATCH 1/7 provides more details on how this set resolve the
confused relationship between <vcpu> and <vcpupin>. This patch
is to implement the codes to inherit <vcpu>'s "cpuset" for
vcpu that doesn't have <vcpupin> specified, and <vcpupin>
for these vcpu will be ignored when formating. Underlying
driver implementation will make sure the vcpu thread pinned
to correct pCPUs.
---
 src/conf/domain_conf.c |   71 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 70 insertions(+), 1 deletions(-)

diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index d8ea8ce..e404a68 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8810,6 +8810,41 @@ static virDomainDefPtr virDomainDefParseXML(virCapsPtr caps,
     }
     VIR_FREE(nodes);
 
+    /* Initialize the pinning policy for vcpus which doesn't has
+     * the policy specified explicitly as def->cpuset.
+     */
+    if (def->cpumask) {
+        if (!def->cputune.vcpupin) {
+            if (VIR_ALLOC_N(def->cputune.vcpupin, def->vcpus) < 0) {
+                virReportOOMError();
+                goto error;
+            }
+        } else {
+            if (VIR_REALLOC_N(def->cputune.vcpupin, def->vcpus) < 0) {
+                virReportOOMError();
+                goto error;
+            }
+        }
+
+        for (i = 0; i < def->vcpus; i++) {
+            if (!virDomainVcpuPinIsDuplicate(def->cputune.vcpupin,
+                                             def->cputune.nvcpupin,
+                                             i)) {
+                virDomainVcpuPinDefPtr vcpupin = NULL;
+
+                if (VIR_ALLOC(vcpupin) < 0) {
+                    virReportOOMError();
+                    goto error;
+                }
+
+                vcpupin->cpumask = virBitmapNew(VIR_DOMAIN_CPUMASK_LEN);
+                virBitmapCopy(vcpupin->cpumask, def->cpumask);
+                vcpupin->vcpuid = i;
+                def->cputune.vcpupin[def->cputune.nvcpupin++] = vcpupin;
+            }
+        }
+    }
+
     if ((n = virXPathNodeSet("./cputune/emulatorpin", ctxt, &nodes)) < 0) {
         virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                        _("cannot extract emulatorpin nodes"));
@@ -13320,6 +13355,31 @@ virDomainHubDefFormat(virBufferPtr buf,
     return 0;
 }
 
+/*
+ * Return true if no <vcpupin> specified in domain XML
+ * (I.e. all vcpus inherit the cpuset from "cpuset" of
+ * <vcpu>). Or false otherwise.
+ */
+static bool
+virDomainIsAllVcpupinInherited(virDomainDefPtr def)
+{
+    int i;
+
+    if (!def->cpumask) {
+        if (!def->cputune.vcpupin)
+            return true;
+        else
+            return false;
+    } else {
+        for (i = 0; i < def->cputune.nvcpupin; i++) {
+            if (!virBitmapEqual(def->cputune.vcpupin[i]->cpumask,
+                                def->cpumask))
+                return false;
+        }
+
+        return true;
+   }
+}
 
 #define DUMPXML_FLAGS                           \
     (VIR_DOMAIN_XML_SECURE |                    \
@@ -13493,7 +13553,8 @@ virDomainDefFormatInternal(virDomainDefPtr def,
         virBufferAsprintf(buf, " current='%u'", def->vcpus);
     virBufferAsprintf(buf, ">%u</vcpu>\n", def->maxvcpus);
 
-    if (def->cputune.shares || def->cputune.vcpupin ||
+    if (def->cputune.shares ||
+        (def->cputune.vcpupin && !virDomainIsAllVcpupinInherited(def)) ||
         def->cputune.period || def->cputune.quota ||
         def->cputune.emulatorpin ||
         def->cputune.emulator_period || def->cputune.emulator_quota)
@@ -13521,6 +13582,14 @@ virDomainDefFormatInternal(virDomainDefPtr def,
 
     if (def->cputune.vcpupin) {
         for (i = 0; i < def->cputune.nvcpupin; i++) {
+            /* Ignore the vcpupin which inherit from "cpuset"
+             * of "<vcpu>."
+             */
+            if (def->cpumask &&
+                virBitmapEqual(def->cpumask,
+                               def->cputune.vcpupin[i]->cpumask))
+                continue;
+
             virBufferAsprintf(buf, "    <vcpupin vcpu='%u' ",
                               def->cputune.vcpupin[i]->vcpuid);
 
-- 
1.7.7.6