diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng
index c26408c400..ae25b9b1bc 100644
--- a/docs/schemas/domaincommon.rng
+++ b/docs/schemas/domaincommon.rng
@@ -467,12 +467,16 @@
         <value>sev</value>
       </attribute>
       <interleave>
-        <element name="cbitpos">
-          <data type="unsignedInt"/>
-        </element>
-        <element name="reducedPhysBits">
-          <data type="unsignedInt"/>
-        </element>
+        <optional>
+          <element name="cbitpos">
+            <data type="unsignedInt"/>
+          </element>
+        </optional>
+        <optional>
+          <element name="reducedPhysBits">
+            <data type="unsignedInt"/>
+          </element>
+        </optional>
         <element name="policy">
           <ref name="hexuint"/>
         </element>
diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
index bbe59f61d0..efa5ac527b 100644
--- a/src/conf/domain_conf.c
+++ b/src/conf/domain_conf.c
@@ -16764,6 +16764,7 @@ virDomainSEVDefParseXML(xmlNodePtr sevNode,
     virDomainSEVDefPtr def;
     unsigned long policy;
     g_autofree char *type = NULL;
+    int rc = -1;
 
     def = g_new0(virDomainSEVDef, 1);
 
@@ -16788,25 +16789,35 @@ virDomainSEVDefParseXML(xmlNodePtr sevNode,
         goto error;
     }
 
-    if (virXPathUInt("string(./cbitpos)", ctxt, &def->cbitpos) < 0) {
-        virReportError(VIR_ERR_XML_ERROR, "%s",
-                       _("failed to get launch security cbitpos"));
-        goto error;
-    }
-
-    if (virXPathUInt("string(./reducedPhysBits)", ctxt,
-                     &def->reduced_phys_bits) < 0) {
-        virReportError(VIR_ERR_XML_ERROR, "%s",
-                       _("failed to get launch security reduced-phys-bits"));
-        goto error;
-    }
-
     if (virXPathULongHex("string(./policy)", ctxt, &policy) < 0) {
         virReportError(VIR_ERR_XML_ERROR, "%s",
                        _("failed to get launch security policy"));
         goto error;
     }
 
+    /* the following attributes are platform dependent and if missing, we can
+     * autofill them from domain capabilities later
+     */
+    rc = virXPathUInt("string(./cbitpos)", ctxt, &def->cbitpos);
+    if (rc == 0) {
+        def->haveCbitpos = true;
+    } else if (rc == -2) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("Invalid format for launch security cbitpos"));
+        goto error;
+    }
+
+    rc = virXPathUInt("string(./reducedPhysBits)", ctxt,
+                      &def->reduced_phys_bits);
+    if (rc == 0) {
+        def->haveReducedPhysBits = true;
+    } else if (rc == -2) {
+        virReportError(VIR_ERR_XML_ERROR, "%s",
+                       _("Invalid format for launch security "
+                         "reduced-phys-bits"));
+        goto error;
+    }
+
     def->policy = policy;
     def->dh_cert = virXPathString("string(./dhCert)", ctxt);
     def->session = virXPathString("string(./session)", ctxt);
@@ -28958,9 +28969,12 @@ virDomainSEVDefFormat(virBufferPtr buf, virDomainSEVDefPtr sev)
                       virDomainLaunchSecurityTypeToString(sev->sectype));
     virBufferAdjustIndent(buf, 2);
 
-    virBufferAsprintf(buf, "<cbitpos>%d</cbitpos>\n", sev->cbitpos);
-    virBufferAsprintf(buf, "<reducedPhysBits>%d</reducedPhysBits>\n",
-                      sev->reduced_phys_bits);
+    if (sev->haveCbitpos)
+        virBufferAsprintf(buf, "<cbitpos>%d</cbitpos>\n", sev->cbitpos);
+
+    if (sev->haveReducedPhysBits)
+        virBufferAsprintf(buf, "<reducedPhysBits>%d</reducedPhysBits>\n",
+                          sev->reduced_phys_bits);
     virBufferAsprintf(buf, "<policy>0x%04x</policy>\n", sev->policy);
     if (sev->dh_cert)
         virBufferEscapeString(buf, "<dhCert>%s</dhCert>\n", sev->dh_cert);
diff --git a/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.x86_64-2.12.0.args b/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.x86_64-2.12.0.args
new file mode 100644
index 0000000000..378c3b681c
--- /dev/null
+++ b/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.x86_64-2.12.0.args
@@ -0,0 +1,37 @@
+LC_ALL=C \
+PATH=/bin \
+HOME=/tmp/lib/domain--1-QEMUGuest1 \
+USER=test \
+LOGNAME=test \
+XDG_DATA_HOME=/tmp/lib/domain--1-QEMUGuest1/.local/share \
+XDG_CACHE_HOME=/tmp/lib/domain--1-QEMUGuest1/.cache \
+XDG_CONFIG_HOME=/tmp/lib/domain--1-QEMUGuest1/.config \
+QEMU_AUDIO_DRV=none \
+/usr/bin/qemu-system-x86_64 \
+-name guest=QEMUGuest1,debug-threads=on \
+-S \
+-object secret,id=masterKey0,format=raw,\
+file=/tmp/lib/domain--1-QEMUGuest1/master-key.aes \
+-machine pc-1.0,accel=kvm,usb=off,dump-guest-core=off,memory-encryption=sev0 \
+-m 214 \
+-realtime mlock=off \
+-smp 1,sockets=1,cores=1,threads=1 \
+-uuid c7a5fdbd-edaf-9455-926a-d65c16db1809 \
+-display none \
+-no-user-config \
+-nodefaults \
+-chardev socket,id=charmonitor,fd=1729,server,nowait \
+-mon chardev=charmonitor,id=monitor,mode=control \
+-rtc base=utc \
+-no-shutdown \
+-no-acpi \
+-boot strict=on \
+-device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 \
+-drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
+-device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 \
+-object sev-guest,id=sev0,cbitpos=47,reduced-phys-bits=1,policy=0x1,\
+dh-cert-file=/tmp/lib/domain--1-QEMUGuest1/dh_cert.base64,\
+session-file=/tmp/lib/domain--1-QEMUGuest1/session.base64 \
+-sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,\
+resourcecontrol=deny \
+-msg timestamp=on
diff --git a/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.xml b/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.xml
new file mode 100644
index 0000000000..41ec4cb872
--- /dev/null
+++ b/tests/qemuxml2argvdata/launch-security-sev-missing-platform-info.xml
@@ -0,0 +1,35 @@
+<domain type='kvm'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc-1.0'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <disk type='block' device='disk'>
+      <driver name='qemu' type='raw'/>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <memballoon model='none'/>
+  </devices>
+  <launchSecurity type='sev'>
+    <policy>0x0001</policy>
+    <dhCert>AQAAAAAOAAAAQAAAAAOAAAAQAAAAAOAAAAQAAAAAOAAAAQAAAAAOAAA</dhCert>
+    <session>IHAVENOIDEABUTJUSTPROVIDINGASTRING</session>
+  </launchSecurity>
+</domain>
diff --git a/tests/qemuxml2argvtest.c b/tests/qemuxml2argvtest.c
index f0f6ae95e5..092e80e9c0 100644
--- a/tests/qemuxml2argvtest.c
+++ b/tests/qemuxml2argvtest.c
@@ -3319,6 +3319,7 @@ mymain(void)
     DO_TEST_CAPS_ARCH_LATEST("vhost-vsock-ccw-auto", "s390x");
 
     DO_TEST_CAPS_VER("launch-security-sev", "2.12.0");
+    DO_TEST_CAPS_VER("launch-security-sev-missing-platform-info", "2.12.0");
 
     DO_TEST_CAPS_LATEST("vhost-user-fs-fd-memory");
     DO_TEST_CAPS_LATEST("vhost-user-fs-hugepages");