[libvirt] [PATCH] Add XML config switch to enable/disable vhost-net support
Daniel P. Berrange
berrange at redhat.com
Fri Jan 14 13:22:16 UTC 2011
On Thu, Jan 13, 2011 at 01:45:28AM -0500, Laine Stump wrote:
> This patch is in response to
>
> https://bugzilla.redhat.com/show_bug.cgi?id=643050
>
> The existing libvirt support for the vhost-net backend to the virtio
> network driver happens automatically - if the vhost-net device is
> available, it is always enabled, otherwise the standard userland
> virtio backend is used.
>
> This patch makes it possible to force whether or not vhost-net is used
> with a bit of XML. Adding a <driver> element to the interface XML, eg:
>
> <interface type="network">
> <model type="virtio"/>
> <driver name="vhost"/>
>
> will force use of vhost-net (if it's not available, the domain will
> fail to start). if driver name="qemu", vhost-net will not be used even
> if it is available.
>
> If there is no <driver name='xxx'/> in the config, libvirt will revert
> to the pre-existing automatic behavior - use vhost-net if it's
> available, and userland backend if vhost-net isn't available.
> ---
>
> Note that I don't really like the "name='vhost|qemu'" nomenclature,
> but am including it here just to get the patches on the list. I could
> live with it this way, or with any of the following (anyone have a
> strong opinion?) (note that in all cases, nothing specified means "try
> to use vhost, but fallback to userland if necessary")
>
> vhost='on|off'
> vhost='required|disabled'
> mode='vhost|qemu'
> mode='kernel|user'
> backend='kernel|user'
I wanted 'name=' becasue that matches <driver> usage in <disk>.
This rules out the first options completely, since we can just
play with attribute values. kernel|user is nice, except when
QEMU invent vhost2, and now 'kernel' is no longer unique :-(
Also we used 'name=qemu' already in <disk> to refer to the
in-QEMU disk backend, and there's likely to be a 'vhost' backend
for disks too in the future. So in summary I think 'name=vhost|qemu'
is the best optionl.
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index b4df38c..04ed502 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -184,6 +184,10 @@ VIR_ENUM_IMPL(virDomainNet, VIR_DOMAIN_NET_TYPE_LAST,
> "internal",
> "direct")
>
> +VIR_ENUM_IMPL(virDomainNetBackend, VIR_DOMAIN_NET_BACKEND_TYPE_LAST,
> + "qemu",
> + "vhost")
> +
> VIR_ENUM_IMPL(virDomainChrChannelTarget,
> VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_LAST,
> "guestfwd",
> @@ -2289,6 +2293,7 @@ virDomainNetDefParseXML(virCapsPtr caps,
> char *address = NULL;
> char *port = NULL;
> char *model = NULL;
> + char *backend = NULL;
> char *filter = NULL;
> char *internal = NULL;
> char *devaddr = NULL;
> @@ -2371,6 +2376,8 @@ virDomainNetDefParseXML(virCapsPtr caps,
> script = virXMLPropString(cur, "path");
> } else if (xmlStrEqual (cur->name, BAD_CAST "model")) {
> model = virXMLPropString(cur, "type");
> + } else if (xmlStrEqual (cur->name, BAD_CAST "driver")) {
> + backend = virXMLPropString(cur, "name");
> } else if (xmlStrEqual (cur->name, BAD_CAST "filterref")) {
> filter = virXMLPropString(cur, "filter");
> VIR_FREE(filterparams);
> @@ -2558,6 +2565,18 @@ virDomainNetDefParseXML(virCapsPtr caps,
> model = NULL;
> }
>
> + if ((backend != NULL) &&
> + (def->model && STREQ(def->model, "virtio"))) {
> + int b;
> + if ((b = virDomainNetBackendTypeFromString(backend)) < 0) {
> + virDomainReportError(VIR_ERR_INTERNAL_ERROR,
> + _("Unkown interface <driver name='%s'> has been specified"),
> + backend);
> + goto error;
> + }
> + def->backend = b;
> + def->backend_specified = 1;
> + }
> if (filter != NULL) {
> switch (def->type) {
> case VIR_DOMAIN_NET_TYPE_ETHERNET:
> @@ -2584,6 +2603,7 @@ cleanup:
> VIR_FREE(script);
> VIR_FREE(bridge);
> VIR_FREE(model);
> + VIR_FREE(backend);
> VIR_FREE(filter);
> VIR_FREE(type);
> VIR_FREE(internal);
> @@ -6275,9 +6295,14 @@ virDomainNetDefFormat(virBufferPtr buf,
> if (def->ifname)
> virBufferEscapeString(buf, " <target dev='%s'/>\n",
> def->ifname);
> - if (def->model)
> + if (def->model) {
> virBufferEscapeString(buf, " <model type='%s'/>\n",
> def->model);
> + if (STREQ(def->model, "virtio") && def->backend_specified) {
> + virBufferVSprintf(buf, " <driver name='%s'/>\n",
> + virDomainNetBackendTypeToString(def->backend));
> + }
> + }
> if (def->filter) {
> virBufferEscapeString(buf, " <filterref filter='%s'",
> def->filter);
> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> index a459a22..451ccad 100644
> --- a/src/conf/domain_conf.h
> +++ b/src/conf/domain_conf.h
> @@ -292,6 +292,13 @@ enum virDomainNetType {
> VIR_DOMAIN_NET_TYPE_LAST,
> };
>
> +/* the backend driver used for virtio interfaces */
> +enum virDomainNetBackendType {
> + VIR_DOMAIN_NET_BACKEND_TYPE_QEMU, /* userland */
> + VIR_DOMAIN_NET_BACKEND_TYPE_VHOST, /* kernel */
> +
> + VIR_DOMAIN_NET_BACKEND_TYPE_LAST,
> +};
>
> /* the mode type for macvtap devices */
> enum virDomainNetdevMacvtapType {
> @@ -310,6 +317,8 @@ struct _virDomainNetDef {
> enum virDomainNetType type;
> unsigned char mac[VIR_MAC_BUFLEN];
> char *model;
> + enum virDomainNetBackendType backend;
> + int backend_specified : 1;
I don't really like this pattern since it is at odds with the way
we handle defaults elsewhere which is to include the default as
the first enum value, eg
enum virDomainNetBackendType {
VIR_DOMAIN_NET_BACKEND_TYPE_DEFAULT, /* Try best available */
VIR_DOMAIN_NET_BACKEND_TYPE_QEMU, /* userland */
VIR_DOMAIN_NET_BACKEND_TYPE_VHOST, /* kernel */
VIR_DOMAIN_NET_BACKEND_TYPE_LAST,
};
And then we do
if (def->backend)
...print XML...
when formatting the XML, so that the 'name=default' never
actually appears in the XML output.
Regards,
Daniel
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