From 96d43ab285395bc2b93683f1d2083e6205fbf664 Mon Sep 17 00:00:00 2001
From: Jonathon Jongsma <jjongsma@redhat.com>
Date: Wed, 9 Feb 2022 15:13:09 -0600
Subject: [PATCH] conf: add support for 'blob' in virtio video device
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Add the ability to enable blob resources for the virtio video device.
This will accelerate the display path due to less or no copying of pixel
data.

Blob resource support can be enabled with e.g.:

    <video>
      <model type='virtio' blob='on'/>
    </video>

Some additional background information about blob resources:
https://lists.freedesktop.org/archives/dri-devel/2020-August/275972.html
https://www.kraxel.org/blog/2021/05/virtio-gpu-qemu-graphics-update/

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2032406

Signed-off-by: Jonathon Jongsma <jjongsma@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
---
 docs/formatdomain.rst             |  7 +++++++
 src/conf/domain_conf.c            |  5 +++++
 src/conf/domain_conf.h            |  1 +
 src/conf/domain_validate.c        | 13 ++++++++++---
 src/conf/schemas/domaincommon.rng |  5 +++++
 5 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index c4077c6868..da059f9aac 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -6437,6 +6437,13 @@ A video device.
    :since:`since 1.3.3` ) extends secondary bar and makes it addressable as
    64bit memory.
 
+   :since:`Since 9.2.0` (QEMU driver only), devices with type "virtio" have an
+   optional ``blob`` attribute that can be set to "on" or "off". Setting
+   ``blob`` to "on" will enable the use of blob resources in the device. This
+   can accelerate the display path by reducing or eliminating copying of pixel
+   data between the guest and host. Note that blob resource support requires
+   QEMU version 6.1 or newer.
+
    :since:`Since 5.9.0` , the ``model`` element may also have an optional
    ``resolution`` sub-element. The ``resolution`` element has attributes ``x``
    and ``y`` to set the minimum resolution for the video device. This
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 8dbab41db8..be1ce1cc53 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -12904,6 +12904,9 @@ virDomainVideoModelDefParseXML(virDomainVideoDef *def,
     if (virXMLPropUIntDefault(node, "heads", 10, VIR_XML_PROP_NONE, &def->heads, 1) < 0)
         return -1;
 
+    if (virXMLPropTristateSwitch(node, "blob", VIR_XML_PROP_NONE, &def->blob) < 0)
+        return -1;
+
     return 0;
 }
 
@@ -25280,6 +25283,8 @@ virDomainVideoDefFormat(virBuffer *buf,
         virBufferAsprintf(buf, " heads='%u'", def->heads);
     if (def->primary)
         virBufferAddLit(buf, " primary='yes'");
+    if (def->blob != VIR_TRISTATE_SWITCH_ABSENT)
+        virBufferAsprintf(buf, " blob='%s'", virTristateSwitchTypeToString(def->blob));
     if (def->accel || def->res) {
         virBufferAddLit(buf, ">\n");
         virBufferAdjustIndent(buf, 2);
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index f5624a0162..5a2c70f012 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -1824,6 +1824,7 @@ struct _virDomainVideoDef {
     bool primary;
     virDomainVideoAccelDef *accel;
     virDomainVideoResolutionDef *res;
+    virTristateSwitch blob;
     virDomainVideoDriverDef *driver;
     virDomainDeviceInfo info;
     virDomainVirtioOptions *virtio;
diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c
index db13e56107..5fb2d4971c 100644
--- a/src/conf/domain_validate.c
+++ b/src/conf/domain_validate.c
@@ -225,9 +225,16 @@ virDomainVideoDefValidate(const virDomainVideoDef *video,
         }
     }
 
-    if (video->type != VIR_DOMAIN_VIDEO_TYPE_VIRTIO &&
-        (virDomainCheckVirtioOptionsAreAbsent(video->virtio) < 0))
-        return -1;
+    if (video->type != VIR_DOMAIN_VIDEO_TYPE_VIRTIO) {
+        if (virDomainCheckVirtioOptionsAreAbsent(video->virtio) < 0)
+            return -1;
+        if (video->blob != VIR_TRISTATE_SWITCH_ABSENT) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("video type '%s' does not support blob resources"),
+                           virDomainVideoTypeToString(video->type));
+            return -1;
+        }
+    }
 
     return 0;
 }
diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index 790bba0f7f..d9373977a8 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -4499,6 +4499,11 @@
                 <ref name="virYesNo"/>
               </attribute>
             </optional>
+            <optional>
+              <attribute name="blob">
+                <ref name="virOnOff"/>
+              </attribute>
+            </optional>
             <optional>
               <element name="acceleration">
                 <optional>