[RFC,v2,03/12] s390x/css: add s390-map-css machine option

Commit Message

Dong Jia Shi Jan. 12, 2017, 7:25 a.m. UTC

From: Xiao Feng Ren <[e-mail]>

We want to support real (i.e. not virtual) channel devices
even for guests that do not support MCSS-E (where guests may
see devices from any channel subsystem image at once). As all
virtio-ccw devices are in css 0xfe (and show up in the default
css 0 for guests not activating MCSS-E), we need an option to
map e.g. passed-through subchannels from their real css (0-3,
or 0 for hosts not activating MCSS-E) into the default css.
This will be exploited in a later patch.

Signed-off-by: Xiao Feng Ren <[e-mail]>
---
 hw/s390x/s390-virtio-ccw.c         | 23 +++++++++++++++++++++++
 include/hw/s390x/s390-virtio-ccw.h |  1 +
 qemu-options.hx                    |  6 +++++-
 target-s390x/cpu.h                 | 10 ++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)

Comments

Dong Jia Shi Feb. 17, 2017, 2:08 a.m. UTC | #1

* Dong Jia Shi <[e-mail]> [2017-01-12 08:25:04 +0100]:

> From: Xiao Feng Ren <[e-mail]>
> 
> We want to support real (i.e. not virtual) channel devices
> even for guests that do not support MCSS-E (where guests may
> see devices from any channel subsystem image at once). As all
> virtio-ccw devices are in css 0xfe (and show up in the default
> css 0 for guests not activating MCSS-E), we need an option to
> map e.g. passed-through subchannels from their real css (0-3,
> or 0 for hosts not activating MCSS-E) into the default css.
> This will be exploited in a later patch.

After some brainstorming, we decided to change this interface a bit.

The first thing is that, we agreed that "s390-squash-mcss" is a better
name than "s390-map-css". The new name denotes that it is trying to
accommodate the devices from multiple channel subsystems into a
non-mcsse-e system, and the word "suqash" is more accurate about what
is happening internally.

The second thing is, we should never map/squash a vfio-ccw device into
css 0xfe, which is reserved for virtio device only. So when squashing,
we need to do it the other way around (i.e. have virtio devices at
0.x.xxxx instead of fe.x.xxxx to accommodate non-mcsse-e).

> 
> Signed-off-by: Xiao Feng Ren <[e-mail]>
[...]

Patch

diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index e340eab..4e8ffda 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -272,6 +272,21 @@  bool cpu_model_allowed(void)
     return true;
 }
 
+static inline bool machine_get_map_css(Object *obj, Error **errp)
+{
+    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
+
+    return ms->s390_map_css;
+}
+
+static inline void machine_set_map_css(Object *obj, bool value,
+                                       Error **errp)
+{
+    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
+
+    ms->s390_map_css = value;
+}
+
 static inline void s390_machine_initfn(Object *obj)
 {
     object_property_add_bool(obj, "aes-key-wrap",
@@ -289,6 +304,14 @@  static inline void s390_machine_initfn(Object *obj)
             "enable/disable DEA key wrapping using the CPACF wrapping key",
             NULL);
     object_property_set_bool(obj, true, "dea-key-wrap", NULL);
+
+    object_property_add_bool(obj, "s390-map-css",
+                             machine_get_map_css,
+                             machine_set_map_css, NULL);
+    object_property_set_description(obj, "s390-map-css",
+            "enable/disable mapping passed-through subchannels into the "
+            "virtual css", NULL);
+    object_property_set_bool(obj, false, "s390-map-css", NULL);
 }
 
 static const TypeInfo ccw_machine_info = {
diff --git a/include/hw/s390x/s390-virtio-ccw.h b/include/hw/s390x/s390-virtio-ccw.h
index 6ecae00..bbc1d21 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -28,6 +28,7 @@  typedef struct S390CcwMachineState {
     /*< public >*/
     bool aes_key_wrap;
     bool dea_key_wrap;
+    bool s390_map_css;
 } S390CcwMachineState;
 
 typedef struct S390CcwMachineClass {
diff --git a/qemu-options.hx b/qemu-options.hx
index c534a2f..293783c 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -43,7 +43,8 @@  DEF("machine", HAS_ARG, QEMU_OPTION_machine, \
     "                dea-key-wrap=on|off controls support for DEA key wrapping (default=on)\n"
     "                suppress-vmdesc=on|off disables self-describing migration (default=off)\n"
     "                nvdimm=on|off controls NVDIMM support (default=off)\n"
-    "                enforce-config-section=on|off enforce configuration section migration (default=off)\n",
+    "                enforce-config-section=on|off enforce configuration section migration (default=off)\n"
+    "                s390-map-css=on|off controls support for mapping into virtual css (default=off)\n",
     QEMU_ARCH_ALL)
 STEXI
 @item -machine [type=]@var{name}[,prop=@var{value}[,...]]
@@ -82,6 +83,9 @@  controls whether DEA wrapping keys will be created to allow
 execution of DEA cryptographic functions.  The default is on.
 @item nvdimm=on|off
 Enables or disables NVDIMM support. The default is off.
+@item s390-map-css=on|off
+Enables or disables mapping passed-through subchannels into the virtual css.
+The default is off.
 @end table
 ETEXI
 
diff --git a/target-s390x/cpu.h b/target-s390x/cpu.h
index fd36a25..85d705d 100644
--- a/target-s390x/cpu.h
+++ b/target-s390x/cpu.h
@@ -1249,6 +1249,16 @@  static inline void s390_crypto_reset(void)
     }
 }
 
+static inline bool s390_get_map_css(void)
+{
+    if (object_property_get_bool(OBJECT(qdev_get_machine()), "s390-map-css",
+                                 NULL)) {
+        return true;
+    }
+
+    return false;
+}
+
 /* machine check interruption code */
 
 /* subclasses */