When the "page-height" attribute of "simple-page-master" is set to auto, it 
generates an infinite loop while trying to conver the fo into a pdf.

<?xml version="1.0" encoding="utf-8"?>
<fo:root xmlns:fo="http://www.w3.org/1999/XSL/Format" 
	xmlns:html="http://www.w3.org/1999/xhtml" 
	writing-mode="lr-tb" hyphenate="false" text-align="justify" 
	role="html:html">
	
<fo:layout-master-set>
	<fo:simple-page-master page-width="21cm" 
				page-height="auto" 
				master-name="all-pages">
		<fo:region-body column-gap="12pt" column-count="1" margin-
left="1in" margin-bottom="1in" margin-right="1in" margin-top="1in"/>
		<fo:region-before display-align="before" extent="1in" region-
name="page-header"/>
		<fo:region-after display-align="after" extent="1in" region-
name="page-footer"/>
		<fo:region-start extent="1in"/>
		<fo:region-end extent="1in"/>
	</fo:simple-page-master>
</fo:layout-master-set>

<fo:page-sequence master-reference="all-pages">
	<fo:title/>

	<fo:static-content flow-name="page-header">
		<fo:block font-size="small" text-align="center" space-
before="0.5in" space-before.conditionality="retain"/>
	</fo:static-content>
	<fo:static-content flow-name="page-footer">
		<fo:block font-size="small" text-align="center" space-
after="0.5in" space-after.conditionality="retain">
			- <fo:page-number/> -
		</fo:block>
	</fo:static-content>

	<fo:flow flow-name="xsl-region-body">
		<fo:block font-family="sans-serif" role="html:body">

		<fo:block space-before="1em" space-after="1em" 
role="html:p">Hello World!</fo:block>

		</fo:block>
	</fo:flow>
</fo:page-sequence>

</fo:root>