[PATCH 1/4] domain_conf: Introduce iothreads XML

[John Ferlan <jferlan@xxxxxxxxxx>]

Introduce XML to allowing adding iothreads to the domain. These can be
used by virtio-blk-pci devices in order to assign a specific thread to
handle the workload for the device.  The iothreads are the official
implementation of the virtio-blk Data Plane that's been in tech preview
for QEMU.

Signed-off-by: John Ferlan <jferlan@xxxxxxxxxx>
---
 docs/formatdomain.html.in     | 26 ++++++++++++++++++++++++++
 docs/schemas/domaincommon.rng | 12 ++++++++++++
 src/conf/domain_conf.c        | 28 ++++++++++++++++++++++++++++
 src/conf/domain_conf.h        |  2 ++
 4 files changed, 68 insertions(+)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index 59127bb..0fe10f4 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -470,6 +470,32 @@
       </dd>
     </dl>
 
+    <h3><a name="elementsIOThreadsAllocation">IOThreads Allocation</a></h3>
+      <p>
+        IOThreads are a QEMU feature that will allow supported disk
+        devices to be configured to use a dedicated event loop thread
+        to handle block I/O requests.
+        <span class="since">Since 1.2.8 (QEMU only)</span>
+      </p>
+
+<pre>
+&lt;domain&gt;
+  ...
+  &lt;iothreads&gt;4&lt;/iothreads&gt;
+  ...
+&lt;/domain&gt;
+</pre>
+
+    <dl>
+      <dt><code>iothreads</code></dt>
+      <dd>
+        The content of this optional element defines the number
+        of IOThreads to be assigned to the domain for use by
+        virtio-blk-pci target storage devices. There should be
+        only 1 or 2 IOThreads per host CPU and 1 IOThread per
+        supported device.
+      </dd>
+    </dl>
 
     <h3><a name="elementsCPUTuning">CPU Tuning</a></h3>
 
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 9a89dd8..b4ac483 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -632,6 +632,12 @@
       </optional>
 
       <optional>
+        <element name="iothreads">
+          <ref name="countIOThreads"/>
+        </element>
+      </optional>
+
+      <optional>
         <ref name="blkiotune"/>
       </optional>
 
@@ -4747,6 +4753,12 @@
       <param name="minInclusive">1</param>
     </data>
   </define>
+  <define name="countIOThreads">
+    <data type="unsignedInt">
+      <param name="pattern">[0-9]+</param>
+      <param name="minInclusive">0</param>
+    </data>
+  </define>
   <define name="vcpuid">
     <data type="unsignedShort">
       <param name="pattern">[0-9]+</param>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 22a7f7e..671c41c 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -11953,6 +11953,23 @@ virDomainDefParseXML(xmlDocPtr xml,
         }
     }
 
+    /* Optional - iothreads */
+    n = virXPathULong("string(./iothreads[1])", ctxt, &count);
+    if (n == -2) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("iothreads count must be an integer"));
+        goto error;
+    } else if (n < 0) {
+        def->iothreads = 0;
+    } else {
+        if ((unsigned int) count != count) {
+            virReportError(VIR_ERR_XML_ERROR,
+                           _("invalid iothreads count '%lu'"), count);
+            goto error;
+        }
+        def->iothreads = count;
+    }
+
     /* Extract cpu tunables. */
     if ((n = virXPathULong("string(./cputune/shares[1])", ctxt,
                            &def->cputune.shares)) < -1) {
@@ -14461,6 +14478,14 @@ virDomainDefCheckABIStability(virDomainDefPtr src,
         goto error;
     }
 
+    if (src->iothreads != dst->iothreads) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Target domain iothreads count %u does not "
+                         "match source %u"),
+                       dst->iothreads, src->iothreads);
+        goto error;
+    }
+
     if (STRNEQ(src->os.type, dst->os.type)) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("Target domain OS type %s does not match source %s"),
@@ -17874,6 +17899,9 @@ virDomainDefFormatInternal(virDomainDefPtr def,
         virBufferAsprintf(buf, " current='%u'", def->vcpus);
     virBufferAsprintf(buf, ">%u</vcpu>\n", def->maxvcpus);
 
+    if (def->iothreads > 0)
+        virBufferAsprintf(buf, "<iothreads>%u</iothreads>\n", def->iothreads);
+
     if (def->cputune.sharesSpecified ||
         (def->cputune.nvcpupin && !virDomainIsAllVcpupinInherited(def)) ||
         def->cputune.period || def->cputune.quota ||
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 36ccf10..705ce32 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1908,6 +1908,8 @@ struct _virDomainDef {
     int placement_mode;
     virBitmapPtr cpumask;
 
+    unsigned int iothreads;
+
     struct {
         unsigned long shares;
         bool sharesSpecified;
-- 
1.9.3

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