From: Peter Krempa <pkrempa@redhat.com>

Add the 'dpofua' setting in the XML and for the qemu driver.

DPO - Disable Page Out and FUA - Force Unit Access are two features
implemented by SCSI disks (either both together or neither of them)
which influence how caching is handled. QEMU provides a good default
but in certain specific occasions changing the default may have
performance benefits.

Add support for setting them via the XML.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
---
 docs/formatdomain.rst                             |  5 +++++
 src/conf/domain_conf.c                            | 15 +++++++++++++++
 src/conf/domain_conf.h                            |  1 +
 src/conf/domain_validate.c                        |  7 +++++++
 src/conf/schemas/domaincommon.rng                 |  5 +++++
 src/qemu/qemu_command.c                           |  1 +
 .../qemuxmlconfdata/disk-scsi.x86_64-latest.args  |  4 ++--
 tests/qemuxmlconfdata/disk-scsi.x86_64-latest.xml |  4 ++--
 tests/qemuxmlconfdata/disk-scsi.xml               |  4 ++--
 9 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/docs/formatdomain.rst b/docs/formatdomain.rst
index c6d0b183d0..1197369481 100644
--- a/docs/formatdomain.rst
+++ b/docs/formatdomain.rst
@@ -3378,6 +3378,11 @@ paravirtualized driver is specified via the ``disk`` element.
    :since:`since after 0.4.4`; "sata" attribute value :since:`since 0.9.7`;
    "removable" attribute value :since:`since 1.1.3`;
    "rotation_rate" attribute value :since:`since 7.3.0`
+   The optional attribute ``dpofua`` (:since:`Since 11.10.0, only QEMU driver`)
+   controls the support of DPO(Disable Page Out) and FUA(Force Unit Access)
+   properties of a SCSI disk cache access (both must be present or absent).
+   If the value is omitted hypervisor default is applied (which may depend on
+   the machine type version) and is the suggested setting.
 ``throttlefilters``
    The optional ``throttlefilters`` element provides the ability to provide additional
    per-device throttle chain :since:`Since 11.2.0`
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index 15d5cd9d80..f6c6c70374 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -8593,6 +8593,10 @@ virDomainDiskDefParseXML(virDomainXMLOption *xmlopt,
         if (virXMLPropUInt(targetNode, "rotation_rate", 10, VIR_XML_PROP_NONE,
                            &def->rotation_rate) < 0)
             return NULL;
+
+        if (virXMLPropTristateSwitch(targetNode, "dpofua", VIR_XML_PROP_NONE,
+                                     &def->dpofua) < 0)
+            return NULL;
     }

     if ((geometryNode = virXPathNode("./geometry", ctxt))) {
@@ -20853,6 +20857,14 @@ virDomainDiskDefCheckABIStability(virDomainDiskDef *src,
         return false;
     }

+    if (src->dpofua != dst->dpofua) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                       _("Target disk 'dpofua' property %1$s does not match source %2$s"),
+                       virTristateSwitchTypeToString(dst->dpofua),
+                       virTristateSwitchTypeToString(src->dpofua));
+        return false;
+    }
+
     if (src->queues != dst->queues) {
         virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
                        _("Target disk queue count %1$u does not match source %2$u"),
@@ -24120,6 +24132,9 @@ virDomainDiskDefFormat(virBuffer *buf,
     }
     if (def->rotation_rate)
         virBufferAsprintf(&childBuf, " rotation_rate='%u'", def->rotation_rate);
+    if (def->dpofua != VIR_TRISTATE_SWITCH_ABSENT)
+        virBufferAsprintf(&childBuf, " dpofua='%s'",
+                          virTristateSwitchTypeToString(def->dpofua));
     virBufferAddLit(&childBuf, "/>\n");

     virDomainDiskDefFormatIotune(&childBuf, def);
diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h
index 11eb46ae53..ccd89e42a6 100644
--- a/src/conf/domain_conf.h
+++ b/src/conf/domain_conf.h
@@ -601,6 +601,7 @@ struct _virDomainDiskDef {
     unsigned int queue_size;
     virDomainDiskModel model;
     virDomainVirtioOptions *virtio;
+    virTristateSwitch dpofua; /* only SCSI disks; control of the DPO/FUA cache setting */

     bool diskElementAuth;
     bool diskElementEnc;
diff --git a/src/conf/domain_validate.c b/src/conf/domain_validate.c
index 8085d782c5..90add3e185 100644
--- a/src/conf/domain_validate.c
+++ b/src/conf/domain_validate.c
@@ -1024,6 +1024,13 @@ virDomainDiskDefValidate(const virDomainDef *def,
         }
     }

+    if (disk->dpofua != VIR_TRISTATE_SWITCH_ABSENT &&
+        disk->bus != VIR_DOMAIN_DISK_BUS_SCSI) {
+        virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s",
+                       _("'dpofua' option is available only for SCSI disks"));
+            return -1;
+    }
+
     return 0;
 }

diff --git a/src/conf/schemas/domaincommon.rng b/src/conf/schemas/domaincommon.rng
index 75b5124c33..4f690837ce 100644
--- a/src/conf/schemas/domaincommon.rng
+++ b/src/conf/schemas/domaincommon.rng
@@ -2615,6 +2615,11 @@
           <ref name="positiveInteger"/>
         </attribute>
       </optional>
+      <optional>
+        <attribute name="dpofua">
+          <ref name="virOnOff"/>
+        </attribute>
+      </optional>
     </element>
   </define>
   <define name="geometry">
diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index c56c321a6e..d0f8d5c5a7 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -1936,6 +1936,7 @@ qemuBuildDiskDeviceProps(const virDomainDef *def,
                               "S:werror", wpolicy,
                               "S:rerror", rpolicy,
                               "A:stats-intervals", &statistics,
+                              "T:dpofua", disk->dpofua, /* SCSI-only, ensured by validation */
                               NULL) < 0)
         return NULL;

diff --git a/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.args b/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.args
index cd07cd2d22..ae0a1ffe0c 100644
--- a/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.args
+++ b/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.args
@@ -41,9 +41,9 @@ XDG_CONFIG_HOME=/var/lib/libvirt/qemu/domain--1-QEMUGuest1/.config \
 -blockdev '{"driver":"file","filename":"/tmp/scsidisk3.img","node-name":"libvirt-3-storage","read-only":false}' \
 -device '{"driver":"scsi-hd","bus":"scsi2.0","channel":0,"scsi-id":0,"lun":0,"device_id":"drive-scsi2-0-0-0","drive":"libvirt-3-storage","id":"scsi2-0-0-0","wwn":5764824127192592812}' \
 -blockdev '{"driver":"file","filename":"/tmp/scsidisk4.img","node-name":"libvirt-2-storage","read-only":false}' \
--device '{"driver":"scsi-hd","bus":"scsi3.0","channel":0,"scsi-id":0,"lun":0,"device_id":"drive-scsi3-0-0-0","drive":"libvirt-2-storage","id":"scsi3-0-0-0"}' \
+-device '{"driver":"scsi-hd","bus":"scsi3.0","channel":0,"scsi-id":0,"lun":0,"device_id":"drive-scsi3-0-0-0","drive":"libvirt-2-storage","id":"scsi3-0-0-0","dpofua":true}' \
 -blockdev '{"driver":"file","filename":"/tmp/scsidisk5.img","node-name":"libvirt-1-storage","read-only":false}' \
--device '{"driver":"scsi-hd","bus":"scsi4.0","channel":0,"scsi-id":0,"lun":0,"device_id":"drive-scsi4-0-0-0","drive":"libvirt-1-storage","id":"scsi4-0-0-0","removable":true}' \
+-device '{"driver":"scsi-hd","bus":"scsi4.0","channel":0,"scsi-id":0,"lun":0,"device_id":"drive-scsi4-0-0-0","drive":"libvirt-1-storage","id":"scsi4-0-0-0","removable":true,"dpofua":false}' \
 -audiodev '{"id":"audio1","driver":"none"}' \
 -device '{"driver":"virtio-balloon-pci","id":"balloon0","bus":"pci.0","addr":"0x6"}' \
 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \
diff --git a/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.xml b/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.xml
index 3e645ea343..33de2a6595 100644
--- a/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.xml
+++ b/tests/qemuxmlconfdata/disk-scsi.x86_64-latest.xml
@@ -46,13 +46,13 @@
     <disk type='file' device='disk'>
       <driver name='qemu' type='raw'/>
       <source file='/tmp/scsidisk4.img'/>
-      <target dev='sdd' bus='scsi'/>
+      <target dev='sdd' bus='scsi' dpofua='on'/>
       <address type='drive' controller='3' bus='0' target='0' unit='0'/>
     </disk>
     <disk type='file' device='disk'>
       <driver name='qemu' type='raw'/>
       <source file='/tmp/scsidisk5.img'/>
-      <target dev='sde' bus='scsi'/>
+      <target dev='sde' bus='scsi' dpofua='off'/>
       <address type='drive' controller='4' bus='0' target='0' unit='0'/>
     </disk>
     <controller type='usb' index='0' model='piix3-uhci'>
diff --git a/tests/qemuxmlconfdata/disk-scsi.xml b/tests/qemuxmlconfdata/disk-scsi.xml
index 755c856b98..7e20c70dfe 100644
--- a/tests/qemuxmlconfdata/disk-scsi.xml
+++ b/tests/qemuxmlconfdata/disk-scsi.xml
@@ -38,12 +38,12 @@
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/scsidisk4.img'/>
-      <target dev='sdd' bus='scsi'/>
+      <target dev='sdd' bus='scsi' dpofua='on'/>
       <address type='drive' controller='3' bus='0' target='0' unit='0'/>
     </disk>
     <disk type='file' device='disk'>
       <source file='/tmp/scsidisk5.img'/>
-      <target dev='sde' bus='scsi' removable='on'/>
+      <target dev='sde' bus='scsi' removable='on' dpofua='off'/>
       <address type='drive' controller='4' bus='0' target='0' unit='0'/>
     </disk>
     <controller type='usb' index='0'/>
-- 
2.51.1