[PATCH v4 5/5] lxc: Count max VCPUs based on cpuset.cpus in native config

[Julio Faracco <jcfaracco@xxxxxxxxx>]

Native config files sometimes can setup cpuset.cpus to pin some CPUs.
Before this, LXC was using a fixed number of 1 VCPU. After this commit,
XML definition will generate a dynamic number of VCPUs based on that
cgroup attribute.

Signed-off-by: Julio Faracco <jcfaracco@xxxxxxxxx>
---
 src/lxc/lxc_container.c                       | 23 ++++++++++++++++++
 src/lxc/lxc_container.h                       |  2 ++
 src/lxc/lxc_native.c                          | 24 +++++++++++++++++--
 .../lxcconf2xml-cpusettune.xml                |  2 +-
 4 files changed, 48 insertions(+), 3 deletions(-)

diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
index 88e27f3060..c5788e5c32 100644
--- a/src/lxc/lxc_container.c
+++ b/src/lxc/lxc_container.c
@@ -2487,3 +2487,26 @@ int lxcContainerChown(virDomainDefPtr def, const char *path)
 
     return 0;
 }
+
+
+int lxcContainerGetMaxCpusInCpuset(const char *cpuset)
+{
+    const char *c = cpuset;
+    int max_cpu = 0;
+
+    while (c) {
+        int a, b, ret;
+
+        ret = sscanf(c, "%d-%d", &a, &b);
+        if (ret == 1)
+            max_cpu++;
+        else if (ret == 2)
+            max_cpu +=  a > b ? a - b + 1 : b - a + 1;
+
+        if (!(c = strchr(c+1, ',')))
+            break;
+        c++;
+    }
+
+    return max_cpu;
+}
diff --git a/src/lxc/lxc_container.h b/src/lxc/lxc_container.h
index 94a6c5309c..6f112e0667 100644
--- a/src/lxc/lxc_container.h
+++ b/src/lxc/lxc_container.h
@@ -63,3 +63,5 @@ virArch lxcContainerGetAlt32bitArch(virArch arch);
 int lxcContainerChown(virDomainDefPtr def, const char *path);
 
 bool lxcIsBasicMountLocation(const char *path);
+
+int lxcContainerGetMaxCpusInCpuset(const char *cpuset);
diff --git a/src/lxc/lxc_native.c b/src/lxc/lxc_native.c
index 02d2bf33e4..409bf00bd2 100644
--- a/src/lxc/lxc_native.c
+++ b/src/lxc/lxc_native.c
@@ -993,6 +993,24 @@ lxcSetCpusetTune(virDomainDefPtr def, virConfPtr properties)
     return 0;
 }
 
+
+static int
+lxcGetVCpuMax(virConfPtr properties)
+{
+    g_autofree char *value = NULL;
+    int vcpumax = 1;
+
+    if (virConfGetValueString(properties, "lxc.cgroup.cpuset.cpus",
+                              &value) > 0) {
+        vcpumax = lxcContainerGetMaxCpusInCpuset(value);
+        if (vcpumax > 0)
+            return vcpumax;
+    }
+
+    return vcpumax;
+}
+
+
 static int
 lxcBlkioDeviceWalkCallback(const char *name, virConfValuePtr value, void *data)
 {
@@ -1132,6 +1150,7 @@ lxcParseConfigString(const char *config,
     virDomainDefPtr vmdef = NULL;
     g_autoptr(virConf) properties = NULL;
     g_autofree char *value = NULL;
+    int vcpumax;
 
     if (!(properties = virConfReadString(config, VIR_CONF_FLAG_LXC_FORMAT)))
         return NULL;
@@ -1155,10 +1174,11 @@ lxcParseConfigString(const char *config,
 
     /* Value not handled by the LXC driver, setting to
      * minimum required to make XML parsing pass */
-    if (virDomainDefSetVcpusMax(vmdef, 1, xmlopt) < 0)
+    vcpumax = lxcGetVCpuMax(properties);
+    if (virDomainDefSetVcpusMax(vmdef, vcpumax, xmlopt) < 0)
         goto error;
 
-    if (virDomainDefSetVcpus(vmdef, 1) < 0)
+    if (virDomainDefSetVcpus(vmdef, vcpumax) < 0)
         goto error;
 
     vmdef->nfss = 0;
diff --git a/tests/lxcconf2xmldata/lxcconf2xml-cpusettune.xml b/tests/lxcconf2xmldata/lxcconf2xml-cpusettune.xml
index 6df089d00f..a1fec12d9b 100644
--- a/tests/lxcconf2xmldata/lxcconf2xml-cpusettune.xml
+++ b/tests/lxcconf2xmldata/lxcconf2xml-cpusettune.xml
@@ -3,7 +3,7 @@
   <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
   <memory unit='KiB'>65536</memory>
   <currentMemory unit='KiB'>65536</currentMemory>
-  <vcpu placement='static' cpuset='1-2,5-7'>1</vcpu>
+  <vcpu placement='static' cpuset='1-2,5-7'>5</vcpu>
   <numatune>
     <memory mode='strict' nodeset='1-4'/>
   </numatune>
-- 
2.20.1