s390x/s390-virtio-ccw: add zpcii-disable machine property

The zpcii-disable machine property can be used to force-disable the use
of zPCI interpretation facilities for a VM.  By default, this setting
will be off for machine 7.2 and newer.

Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Message-Id: <20220902172737.170349-9-mjrosato@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
[thuth: Fix contextual conflict in ccw_machine_7_1_instance_options()]
Signed-off-by: Thomas Huth <thuth@redhat.com>

hw/s390x/s390-pci-kvm.c

@@ -22,7 +22,9 @@
 
 bool s390_pci_kvm_interp_allowed(void)
 {
-    return kvm_s390_get_zpci_op() && !s390_is_pv();
+    return (kvm_s390_get_zpci_op() && !s390_is_pv() &&
+            !object_property_get_bool(OBJECT(qdev_get_machine()),
+                                      "zpcii-disable", NULL));
 }
 
 int s390_pci_kvm_aif_enable(S390PCIBusDevice *pbdev, ZpciFib *fib, bool assist)

hw/s390x/s390-virtio-ccw.c

@@ -645,6 +645,21 @@ static inline void machine_set_dea_key_wrap(Object *obj, bool value,
     ms->dea_key_wrap = value;
 }
 
+static inline bool machine_get_zpcii_disable(Object *obj, Error **errp)
+{
+    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
+
+    return ms->zpcii_disable;
+}
+
+static inline void machine_set_zpcii_disable(Object *obj, bool value,
+                                             Error **errp)
+{
+    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
+
+    ms->zpcii_disable = value;
+}
+
 static S390CcwMachineClass *current_mc;
 
 /*
@@ -740,6 +755,13 @@ static inline void s390_machine_initfn(Object *obj)
             "Up to 8 chars in set of [A-Za-z0-9. ] (lower case chars converted"
             " to upper case) to pass to machine loader, boot manager,"
             " and guest kernel");
+
+    object_property_add_bool(obj, "zpcii-disable",
+                             machine_get_zpcii_disable,
+                             machine_set_zpcii_disable);
+    object_property_set_description(obj, "zpcii-disable",
+            "disable zPCI interpretation facilties");
+    object_property_set_bool(obj, "zpcii-disable", false, NULL);
 }
 
 static const TypeInfo ccw_machine_info = {
@@ -804,10 +826,12 @@ DEFINE_CCW_MACHINE(7_2, "7.2", true);
 static void ccw_machine_7_1_instance_options(MachineState *machine)
 {
     static const S390FeatInit qemu_cpu_feat = { S390_FEAT_LIST_QEMU_V7_1 };
+    S390CcwMachineState *ms = S390_CCW_MACHINE(machine);
 
     ccw_machine_7_2_instance_options(machine);
     s390_cpudef_featoff_greater(16, 1, S390_FEAT_PAIE);
     s390_set_qemu_cpu_model(0x8561, 15, 1, qemu_cpu_feat);
+    ms->zpcii_disable = true;
 }
 
 static void ccw_machine_7_1_class_options(MachineClass *mc)

include/hw/s390x/s390-virtio-ccw.h

@@ -27,6 +27,7 @@ struct S390CcwMachineState {
     bool aes_key_wrap;
     bool dea_key_wrap;
     bool pv;
+    bool zpcii_disable;
     uint8_t loadparm[8];
 };
 

qemu-options.hx

@@ -37,7 +37,8 @@ DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "                memory-encryption=@var{} memory encryption object to use (default=none)\n"
     "                hmat=on|off controls ACPI HMAT support (default=off)\n"
     "                memory-backend='backend-id' specifies explicitly provided backend for main RAM (default=none)\n"
-    "                cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n",
+    "                cxl-fmw.0.targets.0=firsttarget,cxl-fmw.0.targets.1=secondtarget,cxl-fmw.0.size=size[,cxl-fmw.0.interleave-granularity=granularity]\n"
+    "                zpcii-disable=on|off disables zPCI interpretation facilities (default=off)\n",
     QEMU_ARCH_ALL)
 SRST
 ``-machine [type=]name[,prop=value[,...]]``
@@ -157,6 +158,11 @@ SRST
         ::
 
             -machine cxl-fmw.0.targets.0=cxl.0,cxl-fmw.0.targets.1=cxl.1,cxl-fmw.0.size=128G,cxl-fmw.0.interleave-granularity=512k
+
+    ``zpcii-disable=on|off``
+        Disables zPCI interpretation facilties on s390-ccw hosts.
+        This feature can be used to disable hardware virtual assists
+        related to zPCI devices. The default is off.
 ERST
 
 DEF("M", HAS_ARG, QEMU_OPTION_M,

util/qemu-config.c

@@ -236,6 +236,10 @@ static QemuOptsList machine_opts = {
             .help = "Up to 8 chars in set of [A-Za-z0-9. ](lower case chars"
                     " converted to upper case) to pass to machine"
                     " loader, boot manager, and guest kernel",
+        },{
+            .name = "zpcii-disable",
+            .type = QEMU_OPT_BOOL,
+            .help = "disable zPCI interpretation facilities",
         },
         { /* End of list */ }
     }