diff --git a/misc/config_tools/xforms/config.h.xsl b/misc/config_tools/xforms/config.h.xsl
index bab5d7cc4..4255056db 100644
--- a/misc/config_tools/xforms/config.h.xsl
+++ b/misc/config_tools/xforms/config.h.xsl
@@ -7,6 +7,8 @@
     version="1.0"
     xmlns:xi="http://www.w3.org/2003/XInclude"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    xmlns:math="http://exslt.org/math"
+    xmlns:exslt="http://exslt.org/common"
     xmlns:acrn="http://projectacrn.org">
   <xsl:include href="lib.xsl" />
   <xsl:output method="text" />
diff --git a/misc/config_tools/xforms/config.mk.xsl b/misc/config_tools/xforms/config.mk.xsl
index 3620ce9aa..d0176c7eb 100644
--- a/misc/config_tools/xforms/config.mk.xsl
+++ b/misc/config_tools/xforms/config.mk.xsl
@@ -7,6 +7,8 @@
     version="1.0"
     xmlns:xi="http://www.w3.org/2003/XInclude"
     xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+    xmlns:math="http://exslt.org/math"
+    xmlns:exslt="http://exslt.org/common"
     xmlns:acrn="http://projectacrn.org">
   <xsl:include href="lib.xsl" />
   <xsl:output method="text" />
diff --git a/misc/config_tools/xforms/config_common.xsl b/misc/config_tools/xforms/config_common.xsl
index 700b202d3..53ee27da6 100644
--- a/misc/config_tools/xforms/config_common.xsl
+++ b/misc/config_tools/xforms/config_common.xsl
@@ -15,6 +15,14 @@
       <xsl:with-param name="key" select="'BOARD'" />
       <xsl:with-param name="value" select="@board" />
     </xsl:call-template>
+    <xsl:call-template name="integer-by-key-value">
+      <xsl:with-param name="key" select="'MAX_IOAPIC_NUM'" />
+      <xsl:with-param name="value" select="count(//ioapic)" />
+    </xsl:call-template>
+    <xsl:call-template name="integer-by-key-value">
+      <xsl:with-param name="key" select="'MAX_IOAPIC_LINES'" />
+      <xsl:with-param name="value" select="math:max(//gsi_number/text() | exslt:node-set(0))" />
+    </xsl:call-template>
     <xsl:call-template name="msi-msix-max" />
   </xsl:template>
 
@@ -157,18 +165,10 @@
       <xsl:with-param name="value" select="//allocation-data/acrn-config/platform/MAX_PCI_BUS_NUM" />
     </xsl:call-template>
 
-    <xsl:call-template name="integer-by-key">
-      <xsl:with-param name="key" select="'MAX_IOAPIC_NUM'" />
-    </xsl:call-template>
-
     <xsl:call-template name="integer-by-key">
       <xsl:with-param name="key" select="'MAX_PCI_DEV_NUM'" />
     </xsl:call-template>
 
-    <xsl:call-template name="integer-by-key">
-      <xsl:with-param name="key" select="'MAX_IOAPIC_LINES'" />
-    </xsl:call-template>
-
     <xsl:call-template name="integer-by-key">
       <xsl:with-param name="key" select="'MAX_PT_IRQ_ENTRIES'" />
     </xsl:call-template>