Re: [PATCH v6 3/4] conf: introduce dirty_ring_size field

[Hyman]

在 2021/11/22 16:50, Peter Krempa 写道:
On Sat, Nov 20, 2021 at 03:20:47 -0500, huang...@chinatelecom.cn wrote:
From: Hyman Huang(黄勇) <huang...@chinatelecom.cn>

introduce dirty_ring_size in struct "_virDomainDef" to hold
the ring size configured by user, and pass dirty_ring_size
when building qemu commandline if dirty ring feature enabled.

Signed-off-by: Hyman Huang(黄勇) <huang...@chinatelecom.cn>
---
  src/conf/domain_conf.c  | 76 ++++++++++++++++++++++++++++++++++++++++-
  src/conf/domain_conf.h  |  4 +++
  src/qemu/qemu_command.c |  3 ++
  3 files changed, 82 insertions(+), 1 deletion(-)

[...]



@@ -4826,6 +4827,18 @@ virDomainDefPostParseMemtune(virDomainDef *def)
  }
  
  
+static void
+virDomainDefPostParseFeatures(virDomainDef *def)
+{
+    if (def->features[VIR_DOMAIN_FEATURE_KVM] == VIR_TRISTATE_SWITCH_ON &&
+        def->kvm_features[VIR_DOMAIN_KVM_DIRTY_RING] == VIR_TRISTATE_SWITCH_ON 
&&
+        def->dirty_ring_size == 0) {
+        /* set 4096 as default size if dirty ring size not congfigured */

Instead of this quite obvious thing I'd prefer a justification of why
this setting is done in the global post-parse function rather than the
qemu specific one. If there is no good reason to have it globally,
please move it to the qemu-specific one.
Ok, i'll move it into virDomainFeaturesKVMDefParse and parse it once for 
all

+        def->dirty_ring_size = 4096;
+    }
+}

[...]

@@ -17566,8 +17581,10 @@ virDomainFeaturesHyperVDefParse(virDomainDef *def,
  
  static int
  virDomainFeaturesKVMDefParse(virDomainDef *def,
+                            xmlXPathContextPtr ctxt,
                               xmlNodePtr node)
  {
+    xmlNodePtr tmp_node = ctxt->node;

We have an established approach for resetting the XPath context. Please
use it, as ...[1].
Ok

      def->features[VIR_DOMAIN_FEATURE_KVM] = VIR_TRISTATE_SWITCH_ON;
  
      node = xmlFirstElementChild(node);
@@ -17589,9 +17606,37 @@ virDomainFeaturesKVMDefParse(virDomainDef *def,
  
          def->kvm_features[feature] = value;
  
+        /* dirty ring feature should parse size property */
+        if ((virDomainKVM) feature == VIR_DOMAIN_KVM_DIRTY_RING) {
+            if (((virDomainKVM) feature) == VIR_DOMAIN_KVM_DIRTY_RING &&
+                  value == VIR_TRISTATE_SWITCH_ON) {
+                ctxt->node = node;
+
+                if (virXMLPropString(node, "size")) {

virXMLPropString returns an allocated string, so this is leaking memory