[libvirt] [PATCH v2 1/2] Add support for locking domain's memory pages

[Jiri Denemark]

The following XML configuration can be used to request all domain's
memory pages to be kept locked in host's memory (i.e., domain's memory
pages will not be swapped out):

      <memoryBacking>
        <locked/>
      </memoryBacking>
---
 docs/formatdomain.html.in     | 26 ++++++++++++++++----------
 docs/schemas/domaincommon.rng |  5 +++++
 src/conf/domain_conf.c        | 20 +++++++++++---------
 src/conf/domain_conf.h        |  1 +
 4 files changed, 33 insertions(+), 19 deletions(-)

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index c6c0728..a71c484 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -595,22 +595,28 @@
   <memoryBacking>
     <hugepages/>
     <nosharepages/>
+    <locked/>
   </memoryBacking>
   ...
 </domain>
 </pre>
 
+    <p>The optional <code>memoryBacking</code> element may contain several
+      elements that influence how virtual memory pages are backed by host
+      pages.</p>
+
     <dl>
-      <dt><code>memoryBacking</code></dt>
-      <dd>The optional <code>memoryBacking</code> element has two
-        optional elements. The element <code>hugepages</code> tells
-        the hypervisor that the guest should have its memory allocated
-        using hugepages instead of the normal native page size. And the
-        optional element <code>nosharepages</code>
-        (<span class="since">since 1.0.6</span>) tells the hypervisor
-        that share pages (memory merge, KSM) should be disabled on guest
-        startup.
-      </dd>
+      <dt><code>hugepages</code></dt>
+      <dd>This tells the hypervisor that the guest should have its memory
+        allocated using hugepages instead of the normal native page size.</dd>
+      <dt><code>nosharepages</code></dt>
+      <dd>Instructs hypervisor to disable shared pages (memory merge, KSM) for
+        this domain. <span class="since">Since 1.0.6</span></dd>
+      <dt><code>locked</code></dt>
+      <dd>When set and supported by the hypervisor, memory pages belonging
+        to the domain will be locked in host's memory and the host will not
+        be allowed to swap them out.
+        <span class="since">Since 1.0.6</span></dd>
     </dl>
 
 
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 8c7c1bc..018ca0b 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -501,6 +501,11 @@
                 <empty/>
               </element>
             </optional>
+            <optional>
+              <element name="locked">
+                <empty/>
+              </element>
+            </optional>
           </interleave>
         </element>
       </optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 11978db..b5e5d4d 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -10411,6 +10411,9 @@ virDomainDefParseXML(xmlDocPtr xml,
     if ((node = virXPathNode("./memoryBacking/nosharepages", ctxt)))
         def->mem.nosharepages = true;
 
+    if (virXPathBoolean("boolean(./memoryBacking/locked)", ctxt))
+        def->mem.locked = true;
+
     /* Extract blkio cgroup tunables */
     if (virXPathUInt("string(./blkiotune/weight)", ctxt,
                      &def->blkio.weight) < 0)
@@ -15766,17 +15769,16 @@ virDomainDefFormatInternal(virDomainDefPtr def,
         def->mem.swap_hard_limit)
         virBufferAddLit(buf, "  </memtune>\n");
 
-    if (def->mem.hugepage_backed || def->mem.nosharepages)
+    if (def->mem.hugepage_backed || def->mem.nosharepages || def->mem.locked) {
         virBufferAddLit(buf, "  <memoryBacking>\n");
-
-    if (def->mem.hugepage_backed)
-        virBufferAddLit(buf, "    <hugepages/>\n");
-
-    if (def->mem.nosharepages)
-        virBufferAddLit(buf, "    <nosharepages/>\n");
-
-    if (def->mem.hugepage_backed || def->mem.nosharepages)
+        if (def->mem.hugepage_backed)
+            virBufferAddLit(buf, "    <hugepages/>\n");
+        if (def->mem.nosharepages)
+            virBufferAddLit(buf, "    <nosharepages/>\n");
+        if (def->mem.locked)
+            virBufferAddLit(buf, "    <locked/>\n");
         virBufferAddLit(buf, "  </memoryBacking>\n");
+    }
 
     virBufferAddLit(buf, "  <vcpu");
     virBufferAsprintf(buf, " placement='%s'",
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index f40bfc6..a10b2ab 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1863,6 +1863,7 @@ struct _virDomainDef {
         unsigned long long cur_balloon; /* in kibibytes */
         bool hugepage_backed;
         bool nosharepages;
+        bool locked;
         int dump_core; /* enum virDomainMemDump */
         unsigned long long hard_limit; /* in kibibytes */
         unsigned long long soft_limit; /* in kibibytes */
-- 
1.8.2.1