diff --git a/Osstest/HostDB/Executive.pm b/Osstest/HostDB/Executive.pm
index 7ffca6c4..8bedbdff 100644
--- a/Osstest/HostDB/Executive.pm
+++ b/Osstest/HostDB/Executive.pm
@@ -90,6 +90,25 @@ END
     return $flags;
 }
 
+sub set_flag($$$) {
+    my ($hd, $ho, $flag) = @_;
+    my $rmq = $dbh_tests->prepare(<<END);
+        DELETE FROM hostflags WHERE hostname=? AND hostflag=?
+END
+    my $addq = $dbh_tests->prepare(<<END);
+        INSERT INTO hostflags (hostname,hostflag) VALUES (?,?)
+END
+    my $blessing = intended_blessing();
+
+    die "Attempting to modify host flags with intended blessing $blessing != real"
+        if $blessing ne "real";
+
+    db_retry($dbh_tests, [qw(resources)], sub {
+        $rmq->execute($ho->{Name}, $flag);
+        $addq->execute($ho->{Name}, $flag);
+    });
+}
+
 sub get_arch_platforms ($$$) {
     my ($hd, $blessing, $arch, $suite) = @_;
 
diff --git a/Osstest/HostDB/Static.pm b/Osstest/HostDB/Static.pm
index 0c6be3ee..8ac39cf5 100644
--- a/Osstest/HostDB/Static.pm
+++ b/Osstest/HostDB/Static.pm
@@ -72,6 +72,12 @@ sub get_flags ($$) { #method
     return $flags;
 }
 
+sub set_property($$$) {
+    my ($hd, $ho, $flag) = @_;
+
+    die "Cannot set flags in standalone mode for $ho->{Name} $flag\n";
+}
+
 sub get_arch_platforms ($$$) {
     my ($hd, $blessing, $arch, $suite) = @_;
 
diff --git a/Osstest/TestSupport.pm b/Osstest/TestSupport.pm
index f49ed529..0291dbd8 100644
--- a/Osstest/TestSupport.pm
+++ b/Osstest/TestSupport.pm
@@ -84,9 +84,9 @@ BEGIN {
                       get_target_property get_host_native_linux_console
                       hostnamepath hostnamepath_list set_runtime_hostflag
                       power_state power_cycle power_reboot_attempts
-                      serial_fetch_logs set_host_property
+                      serial_fetch_logs set_host_property set_host_flag
                       propname_massage propname_check
-                      hostprop_putative_record
+                      hostprop_putative_record hostflag_putative_record
          
                       get_stashed open_unique_stashfile compress_stashed
                       dir_identify_vcs
@@ -1411,6 +1411,18 @@ sub hostprop_putative_record ($$$) {
     store_runvar("hostprop/$ho->{Ident}/$prop", $val);
 }
 
+sub set_host_flag ($$) {
+    my ($ho,$flag) = @_;
+
+    $mhostdb->set_flag($ho, $flag);
+}
+
+sub hostflag_putative_record ($$) {
+    my ($ho, $prop) = @_;
+
+    store_runvar("hostflag/$ho->{Ident}/$prop", "");
+}
+
 sub get_target_property ($$;$);
 sub get_target_property ($$;$) {
     my ($ho, $prop, $defval) = @_;
diff --git a/sg-run-job b/sg-run-job
index 7c58d4ba..f6bfdfd5 100755
--- a/sg-run-job
+++ b/sg-run-job
@@ -679,6 +679,7 @@ proc examine-host-examine {install} {
     if {$ok} {
 	run-ts -.  =           ts-examine-serial-post + host
 	run-ts .   =           ts-examine-logs-save   + host
+	run-ts .   =           ts-examine-iommu       + host
 	run-ts .   =           ts-examine-hostprops-save
     }
 }
diff --git a/ts-examine-hostprops-save b/ts-examine-hostprops-save
index 55d23392..502c2db2 100755
--- a/ts-examine-hostprops-save
+++ b/ts-examine-hostprops-save
@@ -27,20 +27,25 @@ tsreadconfig();
 
 our $blessing = intended_blessing();
 
-logm("setting host properties");
+logm("setting host properties and flags");
 
 # NB: in order to aid debug only attempt to save the host props on flights
 # with intended real blessing, for the rest just do a dry run.
 our $dry_run = $blessing ne "real";
-logm("not saving host props with intended blessing $blessing != real")
+logm("not saving host props/flags with intended blessing $blessing != real")
     if $dry_run;
 
 foreach my $k (sort keys %r) {
-    next unless $k =~ m/^hostprop\/([^\/]*)\/([^\/]*)$/;
-    my $ho = selecthost($1);
-    my $prop = $2;
-
-    logm("recording for $ho->{Name} $prop=$r{$k}");
-
-    set_host_property($ho, $prop, $r{$k}) if !$dry_run;
+    next unless $k =~ m/^host(prop|flag)\/([^\/]*)\/([^\/]*)$/;
+    my $type = $1;
+    my $ho = selecthost($2);
+    my $prop = $3;
+
+    if ($type == "flag") {
+        logm("recording flag $prop for $ho->{Name}");
+        set_host_flag($ho, $prop) if !$dry_run;
+    } else {
+        logm("recording prop for $ho->{Name} $prop=$r{$k}");
+        set_host_property($ho, $prop, $r{$k}) if !$dry_run;
+    }
 }
diff --git a/ts-examine-iommu b/ts-examine-iommu
new file mode 100755
index 00000000..ae91d4d2
--- /dev/null
+++ b/ts-examine-iommu
@@ -0,0 +1,31 @@
+#!/usr/bin/perl -w
+# This is part of "osstest", an automated testing framework for Xen.
+# Copyright (C) 2009-2020 Citrix Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+use strict qw(vars);
+BEGIN { unshift @INC, qw(.); }
+use Osstest;
+use Osstest::TestSupport;
+
+tsreadconfig();
+
+our ($whhost) = @ARGV;
+$whhost ||= 'host';
+our $ho= selecthost($whhost);
+
+our $has_iommu = !target_cmd_root_status($ho, 'xl info|grep directio', 10);
+logm("$ho->{Ident} iommu: $has_iommu");
+hostflag_putative_record($ho, "iommu") if $has_iommu;
