[libvirt] [PATCH v2 03/16] domain: add rendernode attribute on <accel>

[Marc-André Lureau]

Hi

On Fri, Aug 23, 2019 at 9:05 PM Cole Robinson <crobinso at redhat.com> wrote:
>
> On 8/23/19 12:21 PM, Cole Robinson wrote:
> > From: Marc-André Lureau <marcandre.lureau at redhat.com>
> >
> > vhost-user-gpu helper may accept --render-node option to specify on
> > which GPU should the renderning be done.
> >
>
> What does it do if the user doesn't pass one? Pick one itself, or just
> not use one somehow?

This is left unspecified. So it may probe one itself and use it, or
fallback to full-software.

>
> If it picks one, then we may need to treat this like we treat other
> rendernode instances and autoallocate one if the user doesn't specify,
> otherwise we won't be able to add the path to the cgroup for example, or
> selinux label it if necessary. I'm not sure if that actually applies in
> this case, but it's worth considering.
>

I think we may want to auto-allocate a drm node if the helper accepts
the argument, as it is almost always what you'd want. But then we lose
the ability to *not* specify it. I am fine with that.


> > (by comparison <graphics> rendernode is the target/display rendering)
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau at redhat.com>
> > Signed-off-by: Cole Robinson <crobinso at redhat.com>
>
> Also I see now that I accidentally signed off all these patches, that
> was not intentional. Please strip those from v3
>
> > ---
> >  docs/formatdomain.html.in     |  5 +++++
> >  docs/schemas/domaincommon.rng |  5 +++++
> >  src/conf/domain_conf.c        | 18 +++++++++++++++++-
> >  src/conf/domain_conf.h        |  1 +
> >  4 files changed, 28 insertions(+), 1 deletion(-)
> >
> > diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> > index ec650fbe17..5a4807d937 100644
> > --- a/docs/formatdomain.html.in
> > +++ b/docs/formatdomain.html.in
> > @@ -7059,6 +7059,11 @@ qemu-kvm -net nic,model=? /dev/null
> >          <dd>Enable 3D acceleration (for vbox driver
> >          <span class="since">since 0.7.1</span>, qemu driver
> >          <span class="since">since 1.3.0</span>)</dd>
> > +
> > +        <dt><code>rendernode</code></dt>
> > +        <dd>Absolute path to a host's DRI device to be used for
> > +        rendering (for vhost-user driver only, <span
> > +        class="since">since 5.5.0</span>)</dd>
> >          </dl>
> >        </dd>
> >
> > diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
> > index bac566855d..6e91fe6cef 100644
> > --- a/docs/schemas/domaincommon.rng
> > +++ b/docs/schemas/domaincommon.rng
> > @@ -3644,6 +3644,11 @@
> >                    <ref name="virYesNo"/>
> >                  </attribute>
> >                </optional>
> > +              <optional>
> > +                <attribute name="rendernode">
> > +                  <ref name="absFilePath"/>
> > +                </attribute>
> > +              </optional>
> >              </element>
> >            </optional>
> >          </element>
> > diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> > index f51575d57d..2cc055491d 100644
> > --- a/src/conf/domain_conf.c
> > +++ b/src/conf/domain_conf.c
> > @@ -2832,6 +2832,8 @@ virDomainVideoDefClear(virDomainVideoDefPtr def)
> >
> >      virDomainDeviceInfoClear(&def->info);
> >
> > +    if (def->accel)
> > +        VIR_FREE(def->accel->rendernode);
> >      VIR_FREE(def->accel);
> >      VIR_FREE(def->virtio);
> >      VIR_FREE(def->driver);
> > @@ -15270,6 +15272,7 @@ virDomainVideoAccelDefParseXML(xmlNodePtr node)
> >      int val;
> >      VIR_AUTOFREE(char *) accel2d = NULL;
> >      VIR_AUTOFREE(char *) accel3d = NULL;
> > +    VIR_AUTOFREE(char *) rendernode = NULL;
> >
> >      cur = node->children;
> >      while (cur != NULL) {
> > @@ -15278,12 +15281,13 @@ virDomainVideoAccelDefParseXML(xmlNodePtr node)
> >                  virXMLNodeNameEqual(cur, "acceleration")) {
> >                  accel3d = virXMLPropString(cur, "accel3d");
> >                  accel2d = virXMLPropString(cur, "accel2d");
> > +                rendernode = virXMLPropString(cur, "rendernode");
> >              }
> >          }
> >          cur = cur->next;
> >      }
> >
> > -    if (!accel3d && !accel2d)
> > +    if (!accel3d && !accel2d && !rendernode)
> >          return NULL;
> >
> >      if (VIR_ALLOC(def) < 0)
> > @@ -15307,6 +15311,9 @@ virDomainVideoAccelDefParseXML(xmlNodePtr node)
> >          def->accel2d = val;
> >      }
> >
> > +    if (VIR_STRDUP(def->rendernode, rendernode) < 0)
> > +        goto cleanup;
> > +
>
> Huh, this function has no error reporting? A bogus accel2d/accel3d value
> will raise an error but it never triggers the error path in the calling
> function. Not your fault of course :)
>
> >   cleanup:
> >      return def;
> >  }
> > @@ -15474,6 +15481,11 @@ virDomainVideoDefParseXML(virDomainXMLOptionPtr xmlopt,
> >              goto error;
> >          }
> >      }
> > +    if (!def->vhostuser && def->accel && def->accel->rendernode) {
> > +        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
> > +                       _("unsupported rendernode accel attribute without 'vhost-user'"));
> > +        goto error;
> > +    }
> >
>
> This function doesn't represent best practices, but this style of check
> should be moved to virDomainVideoDefValidate IMO
>
> Thanks,
> Cole
>
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-- 
Marc-André Lureau