[PATCH] Add page_per_vq flag to the 'driver' element of virtio devices

[Jonathon Jongsma]

On Thu, 2021-04-29 at 14:12 +0300, Gavi Teitz wrote:
> https://bugzilla.redhat.com/show_bug.cgi?id=1925363
> 
> Add support for setting the page-per-vq flag, which is important for
> vdpa with vhost-user performance.
> 
> Signed-off-by: Gavi Teitz <gavi at nvidia.com>
> 

[snip]

> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 9d98f48..0350fde 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -10446,6 +10446,7 @@ virDomainNetDefParseXML(virDomainXMLOption
> *xmlopt,
>      g_autofree char *queues = NULL;
>      g_autofree char *rx_queue_size = NULL;
>      g_autofree char *tx_queue_size = NULL;
> +    g_autofree char *page_per_vq = NULL;
>      g_autofree char *filter = NULL;
>      g_autofree char *internal = NULL;
>      g_autofree char *mode = NULL;
> @@ -10615,6 +10616,7 @@ virDomainNetDefParseXML(virDomainXMLOption
> *xmlopt,
>                  queues = virXMLPropString(cur, "queues");
>                  rx_queue_size = virXMLPropString(cur,
> "rx_queue_size");
>                  tx_queue_size = virXMLPropString(cur,
> "tx_queue_size");
> +                page_per_vq = virXMLPropString(cur, "page_per_vq");
>  
>                  if (virDomainVirtioOptionsParseXML(cur, &def-
> >virtio) < 0)
>                      goto error;
> @@ -11041,6 +11043,15 @@ virDomainNetDefParseXML(virDomainXMLOption
> *xmlopt,
>              }
>              def->driver.virtio.tx_queue_size = q;
>          }
> +        if (page_per_vq) {
> +            if ((val = virTristateSwitchTypeFromString(page_per_vq))
> <= 0) {
> +                virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
> +                               _("unknown page_per_vq mode '%s'"),
> +                               page_per_vq);
> +                goto error;
> +            }
> +            def->driver.virtio.page_per_vq = val;
> +        }

Tim Wiederhake has been doing a bunch of refactoring work in this area
changing code like this to use the newish virXMLProp* functions. 

So I think this whole chunk could instead be something like:

if (virXMLPropTristateSwitch(cur, "page_per_vq", VIR_XML_PROP_NONE, 
			     &def->driver.virtio.page_per_vq) < 0)
    return -1;


(untested)

Jonathon