[PATCH v2 2/3] conf: support for virtio-blk-pci discard option

[<yuxiating@xxxxxxxxxx>]

From: yuxiating <yuxiating@xxxxxxxxxx>

DISCARD and WRITE_ZEROES features for machine type >= 4.0 is enabled by default
since 5c81161f8041("virtio-blk: add "discard" and "write-zeroes" properties).
Virtio_blk kernel driver has a bug that causes memory corruption in
virtblk_setup_discard_write_zeroes();
af822aa68fbd ("block: virtio_blk: fix handling single range discard request")
has fix it.
However, some operating systems are not fixed and need to disabled on the
QEMU side.

Signed-off-by: yuxiating <yuxiating@xxxxxxxxxx>
---
 docs/formatdomain.rst         | 3 +++
 docs/schemas/domaincommon.rng | 8 ++++++++
 src/conf/domain_conf.c        | 8 ++++++++
 src/conf/domain_conf.h        | 1 +
 src/conf/domain_validate.c    | 6 ++++++
 5 files changed, 26 insertions(+)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index 479a3acfbb..e579b9f4dc 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -3087,6 +3087,9 @@ paravirtualized driver is specified via the ``disk`` element.
       virtio-blk. ( :since:`Since 3.9.0` )
    -  For virtio disks, `Virtio-specific options <#elementsVirtio>`__ can also
       be set. ( :since:`Since 3.5.0` )
+   -  The optional ``discard_enable`` attribute controls whether to enable the
+      DISCRAD feature of virtio-blk.The value can be either "on" or "off".
+      :since:`Since 7.7.0 (QEMU and KVM only)`
    -  The optional ``metadata_cache`` subelement controls aspects related to the
       format specific caching of storage image metadata. Note that this setting
       applies only on the top level image; the identically named subelement of
diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index 11fa24f398..72576cac01 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -2363,6 +2363,9 @@
           <ref name="positiveInteger"/>
         </attribute>
       </optional>
+      <optional>
+        <ref name="discard_enable"/>
+      </optional>
       <ref name="virtioOptions"/>
       <optional>
         <element name="metadata_cache">
@@ -2468,6 +2471,11 @@
       </choice>
     </attribute>
   </define>
+  <define name="discard_enable">
+    <attribute name='discard_enable'>
+      <ref name="virOnOff"/>
+    </attribute>
+  </define>
   <define name="controller">
     <element name="controller">
       <optional>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 6127513117..304015f42e 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8930,6 +8930,10 @@ virDomainDiskDefDriverParseXML(virDomainDiskDef *def,
     if (virXMLPropUInt(cur, "queues", 10, VIR_XML_PROP_NONE, &def->queues) < 0)
         return -1;
 
+    if (virXMLPropEnum(cur, "discard_enable", virTristateSwitchTypeFromString,
+                       VIR_XML_PROP_NONZERO, &def->discard_enable) < 0)
+        return -1;
+
     return 0;
 }
 
@@ -23416,6 +23420,10 @@ virDomainDiskDefFormatDriver(virBuffer *buf,
     if (disk->queues)
         virBufferAsprintf(&attrBuf, " queues='%u'", disk->queues);
 
+    if (disk->discard_enable)
+        virBufferAsprintf(&attrBuf, " discard_enable='%s'",
+                          virTristateSwitchTypeToString(disk->discard_enable));
+
     virDomainVirtioOptionsFormat(&attrBuf, disk->virtio);
 
     if (disk->src->metadataCacheMaxSize > 0) {
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index c7e6df7981..56cb6e1244 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -589,6 +589,7 @@ struct _virDomainDiskDef {
 
     bool diskElementAuth;
     bool diskElementEnc;
+    virTristateSwitch discard_enable;
 };
 
 
diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c
index 60f7ccdddd..6eb346916a 100644
--- a/src/conf/domain_validate.c
+++ b/src/conf/domain_validate.c
@@ -612,6 +612,12 @@ virDomainDiskDefValidate(const virDomainDef *def,
             return -1;
         }
 
+        if (disk->discard_enable) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                           _("discard_enable attribute in disk driver element is only supported by virtio-blk"));
+            return -1;
+        }
+
         if (disk->event_idx != VIR_TRISTATE_SWITCH_ABSENT) {
             virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
                            _("disk event_idx mode supported only for virtio bus"));
-- 
2.27.0