Re: [PATCH] virtio-scsi: Add virtqueue_size parameter for qemu

[Ján Tomko <jtomko@xxxxxxxxxx>]

On Wed, Feb 28, 2018 at 10:20:28PM +0300, Klim Kireev wrote:
> In QEMU commit 5c0919d02066c3d0eb896c33265ad90101a6a84a
> adds new option virtqueue_size. This Patch allows this option
> to be set in libvirt.
> ---
> docs/formatdomain.html.in |  6 ++++++
> src/conf/domain_conf.c    | 12 ++++++++++++
> src/conf/domain_conf.h    |  1 +
> src/qemu/qemu_command.c   |  3 +++
> 4 files changed, 22 insertions(+)

The XML parser/formatter and the QEMU command line formatter additions
can be easily tested by extending genericxml2xmltest and
qemuxml2argvtest.

> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index 6fd2189cd..2f33b5e70 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -3867,6 +3867,12 @@
>         host.
>         <span class="since">Since 1.2.7 (QEMU and KVM only)</span>
>       </dd>
> +      <dt><code>virtqueue_size</code></dt>
> +      <dd>
> +        The optional <code>virtqueue_size</code> attribute specifies the size of
> +        virtio queue.

Would be nice to mention why the user wants to set it (and to what
value).

Also, "queue_size" should be sufficient as the attribute name (and
increase the chance of us being able to reuse the attribute for
non-virtio controllers).

> +        <span class="since">Since 3.7.0 (QEMU and KVM only)</span>

Libvirt 4.1.0 is already frozen, so the next release where this can
be merged is 4.2.0.

> +      </dd>
>       <dt><code>max_sectors</code></dt>
>       <dd>
>         The optional <code>max_sectors</code> attribute specifies the maximum
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index d96b012b9..36a4deea2 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -9976,6 +9976,7 @@ virDomainControllerDefParseXML(virDomainXMLOptionPtr xmlopt,
>     char *model = NULL;
>     char *queues = NULL;
>     char *cmd_per_lun = NULL;
> +    char *virtqueue_size = NULL;
>     char *max_sectors = NULL;
>     bool processedModel = false;
>     char *modelName = NULL;
> @@ -10035,6 +10036,7 @@ virDomainControllerDefParseXML(virDomainXMLOptionPtr xmlopt,
>                 queues = virXMLPropString(cur, "queues");
>                 cmd_per_lun = virXMLPropString(cur, "cmd_per_lun");
>                 max_sectors = virXMLPropString(cur, "max_sectors");
> +                virtqueue_size = virXMLPropString(cur, "virtqueue_size");
>                 ioeventfd = virXMLPropString(cur, "ioeventfd");
>                 iothread = virXMLPropString(cur, "iothread");
>
> @@ -10089,6 +10091,12 @@ virDomainControllerDefParseXML(virDomainXMLOptionPtr xmlopt,
>         goto error;
>     }
>
> +    if (virtqueue_size && virStrToLong_ui(virtqueue_size, NULL, 10, &def->virtqueue_size) < 0) {
> +        virReportError(VIR_ERR_XML_ERROR,
> +                       _("Malformed 'virtqueue_size' value '%s'"), virtqueue_size);
> +        goto error;
> +    }
> +
>     if (max_sectors && virStrToLong_ui(max_sectors, NULL, 10, &def->max_sectors) < 0) {
>         virReportError(VIR_ERR_XML_ERROR,
>                        _("Malformed 'max_sectors' value %s"), max_sectors);
> @@ -10310,6 +10318,7 @@ virDomainControllerDefParseXML(virDomainXMLOptionPtr xmlopt,
>     VIR_FREE(model);
>     VIR_FREE(queues);
>     VIR_FREE(cmd_per_lun);
> +    VIR_FREE(virtqueue_size);
>     VIR_FREE(max_sectors);
>     VIR_FREE(modelName);
>     VIR_FREE(chassisNr);
> @@ -23293,6 +23302,9 @@ virDomainControllerDriverFormat(virBufferPtr buf,
>     if (def->cmd_per_lun)
>         virBufferAsprintf(&driverBuf, " cmd_per_lun='%u'", def->cmd_per_lun);
>
> +    if (def->virtqueue_size)
> +        virBufferAsprintf(&driverBuf, " virtqueue_size='%u'", def->virtqueue_size);
> +
>     if (def->max_sectors)
>         virBufferAsprintf(&driverBuf, " max_sectors='%u'", def->max_sectors);
>
> diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
> index 368f16f3f..141bd1aca 100644
> --- a/src/conf/domain_conf.h
> +++ b/src/conf/domain_conf.h
> @@ -816,6 +816,7 @@ struct _virDomainControllerDef {
>     int model; /* -1 == undef */
>     unsigned int queues;
>     unsigned int cmd_per_lun;
> +    unsigned int virtqueue_size;
>     unsigned int max_sectors;
>     int ioeventfd; /* enum virTristateSwitch */
>     unsigned int iothread; /* unused = 0, > 0 specific thread # */
> diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
> index fa0aa5d5c..9b1affd30 100644
> --- a/src/qemu/qemu_command.c
> +++ b/src/qemu/qemu_command.c
> @@ -2808,6 +2808,9 @@ qemuBuildControllerDevStr(const virDomainDef *domainDef,
>     if (def->queues)
>         virBufferAsprintf(&buf, ",num_queues=%u", def->queues);
>
> +    if (def->virtqueue_size)
> +        virBufferAsprintf(&buf, ",virtqueue_size=%u", def->virtqueue_size);
> +

If this option is not supported by the QEMU binary, it would be nice to
report an error before trying to run the domain.

See src/qemu/qemu_capabilities.c and qemuDomainDeviceDefValidateController

Jan

>     if (def->cmd_per_lun)
>         virBufferAsprintf(&buf, ",cmd_per_lun=%u", def->cmd_per_lun);

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