[PATCH 1/3] conf: Add support for virtio-net.rx_queue_size

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https://bugzilla.redhat.com/show_bug.cgi?id=1366989

Qemu grew yet another virtio-net tunable [1]. It basically allows
users to set the size of RX virtio ring. But because virtio-net
uses two separate ring buffers to pass data from/to guest they
named it explicitly rx_queue_size. We should expose it in our XML
too.

1: http://lists.nongnu.org/archive/html/qemu-devel/2016-08/msg02029.html

Signed-off-by: Michal Privoznik <mprivozn@xxxxxxxxxx>
---
 docs/formatdomain.html.in                          |  7 +++++-
 docs/schemas/domaincommon.rng                      |  5 ++++
 src/conf/domain_conf.c                             | 16 ++++++++++++
 src/conf/domain_conf.h                             |  1 +
 src/qemu/qemu_domain.c                             |  7 ++++++
 .../qemuxml2argv-net-virtio-rxqueuesize.xml        | 29 ++++++++++++++++++++++
 6 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize.xml

diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
index bfbb0f2..6642dc8 100644
--- a/docs/formatdomain.html.in
+++ b/docs/formatdomain.html.in
@@ -4604,7 +4604,7 @@ qemu-kvm -net nic,model=? /dev/null
       &lt;source network='default'/&gt;
       &lt;target dev='vnet1'/&gt;
       &lt;model type='virtio'/&gt;
-      <b>&lt;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5'&gt;
+      <b>&lt;driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5' rxqueuesize='128'&gt;
         &lt;host csum='off' gso='off' tso4='off' tso6='off' ecn='off' ufo='off' mrg_rxbuf='off'/&gt;
         &lt;guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/&gt;
       &lt;/driver&gt;
@@ -4720,6 +4720,11 @@ qemu-kvm -net nic,model=? /dev/null
         <span class="since">virtio-net since 1.0.6 (QEMU and KVM only)</span>
         <span class="since">vhost-user since 1.2.17 (QEMU and KVM only)</span>
       </dd>
+      <dt><code>rxqueuesize</code></dt>
+      <dd>
+        The optional <code>rxqueuesize</code> attribute controls
+        the size of virtio ring for each queue as described above.
+      </dd>
     </dl>
     <p>
       Offloading options for the host and guest can be configured using
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 052f28c..4b89a86 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -2529,6 +2529,11 @@
                 </attribute>
               </optional>
               <optional>
+                <attribute name='rxqueuesize'>
+                  <ref name='positiveInteger'/>
+                </attribute>
+              </optional>
+              <optional>
                 <attribute name="txmode">
                   <choice>
                     <value>iothread</value>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 14d4f7d..08cde19 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8911,6 +8911,7 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
     char *ioeventfd = NULL;
     char *event_idx = NULL;
     char *queues = NULL;
+    char *rxqueuesize = NULL;
     char *str = NULL;
     char *filter = NULL;
     char *internal = NULL;
@@ -9083,6 +9084,7 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
                 ioeventfd = virXMLPropString(cur, "ioeventfd");
                 event_idx = virXMLPropString(cur, "event_idx");
                 queues = virXMLPropString(cur, "queues");
+                rxqueuesize = virXMLPropString(cur, "rxqueuesize");
             } else if (xmlStrEqual(cur->name, BAD_CAST "filterref")) {
                 if (filter) {
                     virReportError(VIR_ERR_XML_ERROR, "%s",
@@ -9466,6 +9468,17 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
             if (q > 1)
                 def->driver.virtio.queues = q;
         }
+        if (rxqueuesize) {
+            unsigned int q;
+            if (virStrToLong_uip(rxqueuesize, NULL, 10, &q) < 0) {
+                virReportError(VIR_ERR_XML_DETAIL,
+                               _("'rxqueuesize' attribute must be positive number: %s"),
+                               rxqueuesize);
+                goto error;
+            }
+            if (q > 1)
+                def->driver.virtio.rxqueuesize = q;
+        }
         if ((str = virXPathString("string(./driver/host/@csum)", ctxt))) {
             if ((val = virTristateSwitchTypeFromString(str)) <= 0) {
                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
@@ -9646,6 +9659,7 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
     VIR_FREE(ioeventfd);
     VIR_FREE(event_idx);
     VIR_FREE(queues);
+    VIR_FREE(rxqueuesize);
     VIR_FREE(str);
     VIR_FREE(filter);
     VIR_FREE(type);
@@ -20768,6 +20782,8 @@ virDomainVirtioNetDriverFormat(char **outstr,
     }
     if (def->driver.virtio.queues)
         virBufferAsprintf(&buf, "queues='%u' ", def->driver.virtio.queues);
+    if (def->driver.virtio.rxqueuesize)
+        virBufferAsprintf(&buf, "rxqueuesize='%u' ", def->driver.virtio.rxqueuesize);
 
     virBufferTrim(&buf, " ", -1);
 
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 8b26724..9197d70 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -906,6 +906,7 @@ struct _virDomainNetDef {
             virTristateSwitch ioeventfd;
             virTristateSwitch event_idx;
             unsigned int queues; /* Multiqueue virtio-net */
+            unsigned int rxqueuesize; /* rx_queue_size */
             struct {
                 virTristateSwitch csum;
                 virTristateSwitch gso;
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 6c0f261..ee24086 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -2372,6 +2372,13 @@ qemuDomainDeviceDefValidate(const virDomainDeviceDef *dev,
                              "not supported by QEMU"));
             goto cleanup;
         }
+
+        if (STREQ_NULLABLE(net->model, "virtio") &&
+            net->driver.virtio.rxqueuesize & (net->driver.virtio.rxqueuesize -1)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("rxqueuesize has to be a power of two"));
+            goto cleanup;
+        }
     }
 
     ret = 0;
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize.xml b/tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize.xml
new file mode 100644
index 0000000..e23d3e3
--- /dev/null
+++ b/tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize.xml
@@ -0,0 +1,29 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <interface type='user'>
+      <mac address='00:11:22:33:44:55'/>
+      <model type='virtio'/>
+      <driver rxqueuesize='128'/>
+    </interface>
+    <memballoon model='virtio'/>
+  </devices>
+</domain>
-- 
2.8.4

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