x86/iommu: fix PVH dom0 settings

PVH dom0 must operate with the iommu settings in 'strict' mode i.e. only the
domain's own pages will be mapped in the IOMMU. The check_hwdom_reqs() is
supposed to ensure this. Unfortunately the test for a PVH dom0 is made
using paging_mode_translate() and, when commit f89f5558 "remove late
(on-demand) construction of IOMMU page tables" moved the call of
check_hwdom_reqs() from iommu_hwdom_init() to iommu_domain_init(), that
test became ineffective (because iommu_domain_init() is called before
paging_enable()).

This patch replaces the test of paging_mode_translate() with a test of
hap_enabled(), and also verifies 'strict' mode is turned on in
arch_iommu_check_autotranslated_hwdom().

Reported-by: Roger Pau Monne <roger.pau@citrix.com>
Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Release-acked-by: Juergen Gross <jgross@suse.com>

xen/drivers/passthrough/iommu.c

@@ -154,13 +154,13 @@ custom_param("dom0-iommu", parse_dom0_iommu_param);
 
 static void __hwdom_init check_hwdom_reqs(struct domain *d)
 {
-    if ( iommu_hwdom_none || !paging_mode_translate(d) )
+    if ( iommu_hwdom_none || !hap_enabled(d) )
         return;
 
-    arch_iommu_check_autotranslated_hwdom(d);
-
     iommu_hwdom_passthrough = false;
     iommu_hwdom_strict = true;
+
+    arch_iommu_check_autotranslated_hwdom(d);
 }
 
 int iommu_domain_init(struct domain *d, unsigned int opts)

xen/drivers/passthrough/x86/iommu.c

@@ -85,6 +85,9 @@ void __hwdom_init arch_iommu_check_autotranslated_hwdom(struct domain *d)
 {
     if ( !is_iommu_enabled(d) )
         panic("Presently, iommu must be enabled for PVH hardware domain\n");
+
+    if ( !iommu_hwdom_strict )
+        panic("PVH hardware domain iommu must be set in 'strict' mode\n");
 }
 
 int arch_iommu_domain_init(struct domain *d)