s390x/s390-virtio-ccw: Switch off zPCI enhancements on older machines

zPCI enhancement features (interpretation and forward assist) were
recently introduced to improve performance on PCI passthrough devices.
To maintain the same behaviour on older Z machines, deactivate the
features with the associated properties.

Signed-off-by: Cédric Le Goater <clg@redhat.com>
Message-Id: <20221107161349.1032730-3-clg@kaod.org>
Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index bb98d40792f5010cebdab072edacb44220d63985..7d80bc1837167f04a293296778623e5f37973ce3 100644 (file)
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -844,9 +844,14 @@ static void ccw_machine_7_1_instance_options(MachineState *machine)
 static void ccw_machine_7_1_class_options(MachineClass *mc)
 {
     S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
+    static GlobalProperty compat[] = {
+        { TYPE_S390_PCI_DEVICE, "interpret", "off", },
+        { TYPE_S390_PCI_DEVICE, "forwarding-assist", "off", },
+    };
 
     ccw_machine_7_2_class_options(mc);
     compat_props_add(mc->compat_props, hw_compat_7_1, hw_compat_7_1_len);
+    compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
     s390mc->max_threads = S390_MAX_CPUS;
 }
 DEFINE_CCW_MACHINE(7_1, "7.1", false);