[libvirt] [PATCH v2 1/3] conf: Add support for virtio-net.rx_queue_size

[Martin Kletzander]

On Wed, Aug 31, 2016 at 05:10:33PM +0200, Michal Privoznik wrote:
>https://bugzilla.redhat.com/show_bug.cgi?id=1366989
>
>QEMU added 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 at redhat.com>
>---
> docs/formatdomain.html.in                          | 16 ++++++++-
> docs/schemas/domaincommon.rng                      |  5 +++
> src/conf/domain_conf.c                             | 16 +++++++++
> src/conf/domain_conf.h                             |  1 +
> src/qemu/qemu_domain.c                             |  7 ++++
> ...ml2argv-net-virtio-rxqueuesize-invalid-size.xml | 29 +++++++++++++++
> .../qemuxml2argv-net-virtio-rxqueuesize.xml        | 29 +++++++++++++++
> tests/qemuxml2argvtest.c                           |  1 +
> .../qemuxml2xmlout-net-virtio-rxqueuesize.xml      | 41 ++++++++++++++++++++++
> tests/qemuxml2xmltest.c                            |  1 +
> 10 files changed, 145 insertions(+), 1 deletion(-)
> create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize-invalid-size.xml
> create mode 100644 tests/qemuxml2argvdata/qemuxml2argv-net-virtio-rxqueuesize.xml
> create mode 100644 tests/qemuxml2xmloutdata/qemuxml2xmlout-net-virtio-rxqueuesize.xml
>
>diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
>index 8c15a73..be19bb9 100644
>--- a/docs/formatdomain.html.in
>+++ b/docs/formatdomain.html.in
>@@ -4650,7 +4650,7 @@ qemu-kvm -net nic,model=? /dev/null
>       <source network='default'/>
>       <target dev='vnet1'/>
>       <model type='virtio'/>
>-      <b><driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5'>
>+      <b><driver name='vhost' txmode='iothread' ioeventfd='on' event_idx='off' queues='5' rx_queue_size='256'>
>         <host csum='off' gso='off' tso4='off' tso6='off' ecn='off' ufo='off' mrg_rxbuf='off'/>
>         <guest csum='off' tso4='off' tso6='off' ecn='off' ufo='off'/>
>       </driver>
>@@ -4766,6 +4766,20 @@ 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>rx_queue_size</code></dt>
>+      <dd>
>+        The optional <code>rx_queue_size</code> attribute controls
>+        the size of virtio ring for each queue as described above.
>+        The default value is hypervisor dependent and may change
>+        across its releases. Moreover, some hypervisors may pose
>+        some restrictions on actual value. For instance, latest

I wonder how long this "latest" will be true.  Either say "latest as of
yyyy-mm-dd" or QEMU version or just leave the example out.

>diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
>index 61f6dbb..05a1227 100644
>--- a/src/conf/domain_conf.c
>+++ b/src/conf/domain_conf.c
>@@ -9517,6 +9519,17 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
>             if (q > 1)
>                 def->driver.virtio.queues = q;
>         }
>+        if (rx_queue_size) {
>+            unsigned int q;
>+            if (virStrToLong_uip(rx_queue_size, NULL, 10, &q) < 0) {
>+                virReportError(VIR_ERR_XML_DETAIL,
>+                               _("'rx_queue_size' attribute must be positive number: %s"),
>+                               rx_queue_size);
>+                goto error;
>+            }
>+            if (q > 1)
>+                def->driver.virtio.rx_queue_size = q;

Pointless condition, you can assign it unconditionally.

>+        }
>         if ((str = virXPathString("string(./driver/host/@csum)", ctxt))) {
>             if ((val = virTristateSwitchTypeFromString(str)) <= 0) {
>                 virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
>@@ -9697,6 +9710,7 @@ virDomainNetDefParseXML(virDomainXMLOptionPtr xmlopt,
>     VIR_FREE(ioeventfd);
>     VIR_FREE(event_idx);
>     VIR_FREE(queues);
>+    VIR_FREE(rx_queue_size);
>     VIR_FREE(str);
>     VIR_FREE(filter);
>     VIR_FREE(type);
>@@ -20890,6 +20904,8 @@ virDomainVirtioNetDriverFormat(char **outstr,
>     }
>     if (def->driver.virtio.queues)
>         virBufferAsprintf(&buf, "queues='%u' ", def->driver.virtio.queues);
>+    if (def->driver.virtio.rx_queue_size)
>+        virBufferAsprintf(&buf, "rx_queue_size='%u' ", def->driver.virtio.rx_queue_size);

Long line.

>diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
>index c1fb771..29ade0e 100644
>--- a/src/qemu/qemu_domain.c
>+++ b/src/qemu/qemu_domain.c
>@@ -2475,6 +2475,13 @@ qemuDomainDeviceDefValidate(const virDomainDeviceDef *dev,
>                              "not supported by QEMU"));
>             goto cleanup;
>         }
>+
>+        if (STREQ_NULLABLE(net->model, "virtio") &&
>+            net->driver.virtio.rx_queue_size & (net->driver.virtio.rx_queue_size - 1)) {
>+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
>+                           _("rx_queue_size has to be a power of two"));
>+            goto cleanup;
>+        }

No heck for the boundaries that you mentioned in the example?  I would
expect that boundaries to be checked when they are written there.  I
understand that it doesn't make sense since we can't know them and
adjusting them after every change in qemu is plain wrong.  I guess I
just wanted to say I was surprised =)

ACK with those first three things fixed.

Martin
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