From 757203ee523c8709291f05dd4ad6dbe49809f74b Mon Sep 17 00:00:00 2001
From: Peter Krempa <pkrempa@redhat.com>
Date: Wed, 30 Oct 2019 16:54:56 +0100
Subject: [PATCH] conf: domcaps: Add 'backingStoreInput' domain capability
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Historically we've only supported the <backingStore> as an output-only
element for domain disks. The documentation states that it may become
supported on input. To allow management apps detectin once that happens
add a domain capability which will be asserted if the hypervisor driver
will be able to obey the <backingStore> as configured on input.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
---
 docs/formatdomaincaps.html.in  | 8 ++++++++
 docs/schemas/domaincaps.rng    | 9 +++++++++
 src/conf/domain_capabilities.c | 1 +
 src/conf/domain_capabilities.h | 1 +
 4 files changed, 19 insertions(+)

diff --git a/docs/formatdomaincaps.html.in b/docs/formatdomaincaps.html.in
index 0488d986ee..0bafb67705 100644
--- a/docs/formatdomaincaps.html.in
+++ b/docs/formatdomaincaps.html.in
@@ -516,6 +516,7 @@
     &lt;/gic&gt;
     &lt;vmcoreinfo supported='yes'/&gt;
     &lt;genid supported='yes'/&gt;
+    &lt;backingStoreInput supported='yes'/&gt;
     &lt;sev&gt;
       &lt;cbitpos&gt;47&lt;/cbitpos&gt;
       &lt;reduced-phys-bits&gt;1&lt;/reduced-phys-bits&gt;
@@ -552,6 +553,13 @@
 
     <p>Reports whether the genid feature can be used by the domain.</p>
 
+    <h4><a id="featureBackingStoreInput">backingStoreInput</a></h4>
+
+    <p>Reports whether the hypervisor will obey the &lt;backingStore&gt;
+    elements configured for a &lt;disk&gt; when booting the guest, hotplugging
+    the disk to a running guest, or similar.
+    </p>
+
     <h4><a id="elementsSEV">SEV capabilities</a></h4>
 
     <p>AMD Secure Encrypted Virtualization (SEV) capabilities are exposed under
diff --git a/docs/schemas/domaincaps.rng b/docs/schemas/domaincaps.rng
index 3525c0eeef..88b545ec2a 100644
--- a/docs/schemas/domaincaps.rng
+++ b/docs/schemas/domaincaps.rng
@@ -207,6 +207,9 @@
       <optional>
         <ref name='vmgenid'/>
       </optional>
+      <optional>
+        <ref name='backingStoreInput'/>
+      </optional>
       <optional>
         <ref name='sev'/>
       </optional>
@@ -232,6 +235,12 @@
     </element>
   </define>
 
+  <define name='backingStoreInput'>
+    <element name='backingStoreInput'>
+      <ref name='supported'/>
+    </element>
+  </define>
+
   <define name='sev'>
     <element name='sev'>
       <ref name='supported'/>
diff --git a/src/conf/domain_capabilities.c b/src/conf/domain_capabilities.c
index fa27e95e1b..ca208f2340 100644
--- a/src/conf/domain_capabilities.c
+++ b/src/conf/domain_capabilities.c
@@ -40,6 +40,7 @@ VIR_ENUM_IMPL(virDomainCapsFeature,
               "iothreads",
               "vmcoreinfo",
               "genid",
+              "backingStoreInput",
 );
 
 static virClassPtr virDomainCapsClass;
diff --git a/src/conf/domain_capabilities.h b/src/conf/domain_capabilities.h
index c8eeb035ac..4ec9fe006c 100644
--- a/src/conf/domain_capabilities.h
+++ b/src/conf/domain_capabilities.h
@@ -162,6 +162,7 @@ typedef enum {
     VIR_DOMAIN_CAPS_FEATURE_IOTHREADS = 0,
     VIR_DOMAIN_CAPS_FEATURE_VMCOREINFO,
     VIR_DOMAIN_CAPS_FEATURE_GENID,
+    VIR_DOMAIN_CAPS_FEATURE_BACKING_STORE_INPUT,
 
     VIR_DOMAIN_CAPS_FEATURE_LAST
 } virDomainCapsFeature;