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<p class="MsoNormal">Hi,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">The page-per-vq flag is important for vdpa with vhost-user performance [1].<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Currently there is no way in libvirt to set it in the xml page-per-vq except with qemu args, like so:<span style="font-size:12.0pt;font-family:"Courier New";color:black"><o:p></o:p></span></p>
<p class="MsoNoSpacing"> <devices><o:p></o:p></p>
<p class="MsoNoSpacing"> <interface type='vhostuser'><o:p></o:p></p>
<p class="MsoNoSpacing"> <mac address='fa:16:3e:92:6d:79'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <source type='unix' path='/var/lib/vhost_sockets/sock7f9a971a-cf3' mode='server'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <model type='virtio'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <driver queues='4' rx_queue_size='512' tx_queue_size='512'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <alias name='net0'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/><o:p></o:p></p>
<p class="MsoNoSpacing"> </interface><o:p></o:p></p>
<p class="MsoNoSpacing"> </devices><o:p></o:p></p>
<p class="MsoNoSpacing"> <qemu:commandline><o:p></o:p></p>
<p class="MsoNoSpacing"> <qemu:arg value='-set'/><o:p></o:p></p>
<p class="MsoNoSpacing"> <qemu:arg value='device.net0.page-per-vq=on'/><o:p></o:p></p>
<p class="MsoNoSpacing"> </qemu:commandline><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">However, this is not an approach which can be used for hotplug devices, as qemu:commandline arguments cannot be used for them, and is therefore not suitable for production.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We propose to add the flag to the ‘<span style="font-size:13.5pt;font-family:"LibvirtOverpass",serif;color:black;background:white"> </span><span class="docutils"><span style="font-family:"Courier New";color:black;background:#EEEEEE">driver</span></span>’
element of virtio devices, as this is an attribute related to the virtio transport [2]. This will enable configuring virtio devices with the page-per-vq flag without relying on qemu:commandline arguments.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Are there any issues that would prevent this feature from being accepted?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal">Gavi<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">[1] - <a href="http://doc.dpdk.org/guides/sample_app_ug/vdpa.html">
http://doc.dpdk.org/guides/sample_app_ug/vdpa.html</a> - look for page-per-vq<o:p></o:p></p>
<p class="MsoNormal">[2] - <a href="https://libvirt.org/formatdomain.html#virtio-related-options">
https://libvirt.org/formatdomain.html#virtio-related-options</a><o:p></o:p></p>
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