On 09/05/2024 19.00, Paolo Bonzini wrote:
The CSS subsystem uses global variables, just face the truth and use
a variable also for whether the CSS vmstate is in use; remove the
indirection of fetching it from the machine type, which makes the
TCG code depend unnecessarily on the virtio-ccw machine.

Signed-off-by: Paolo Bonzini <pbonz...@redhat.com>
---
  include/hw/s390x/css.h             |  6 ++++++
  include/hw/s390x/s390-virtio-ccw.h |  7 -------
  hw/s390x/css.c                     | 10 +++++++---
  hw/s390x/s390-virtio-ccw.c         | 15 +++------------
  4 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
index ba72ee3dd20..8289e458370 100644
--- a/include/hw/s390x/css.h
+++ b/include/hw/s390x/css.h
@@ -333,4 +333,10 @@ static inline int ccw_dstream_read_buf(CcwDataStream *cds, 
void *buff, int len)
  #define ccw_dstream_read(cds, v) ccw_dstream_read_buf((cds), &(v), sizeof(v))
  #define ccw_dstream_write(cds, v) ccw_dstream_write_buf((cds), &(v), 
sizeof(v))
+/**
+ * true if (vmstate based) migration of the channel subsystem
+ * is enabled, false if it is disabled.
+ */
+extern bool css_migration_enabled;
+
  #endif
diff --git a/include/hw/s390x/s390-virtio-ccw.h 
b/include/hw/s390x/s390-virtio-ccw.h
index c1d46e78af8..c0494e511cb 100644
--- a/include/hw/s390x/s390-virtio-ccw.h
+++ b/include/hw/s390x/s390-virtio-ccw.h
@@ -43,7 +43,6 @@ struct S390CcwMachineClass {
      /*< public >*/
      bool ri_allowed;
      bool cpu_model_allowed;
-    bool css_migration_enabled;
      bool hpage_1m_allowed;
      int max_threads;
  };
@@ -55,10 +54,4 @@ bool cpu_model_allowed(void);
  /* 1M huge page mappings allowed by the machine */
  bool hpage_1m_allowed(void);
-/**
- * Returns true if (vmstate based) migration of the channel subsystem
- * is enabled, false if it is disabled.
- */
-bool css_migration_enabled(void);
-
  #endif
diff --git a/hw/s390x/css.c b/hw/s390x/css.c
index 295530963a6..b2d5327dbf4 100644
--- a/hw/s390x/css.c
+++ b/hw/s390x/css.c
@@ -23,6 +23,8 @@
  #include "hw/s390x/s390-virtio-ccw.h"
  #include "hw/s390x/s390-ccw.h"
+bool css_migration_enabled = true;
+
  typedef struct CrwContainer {
      CRW crw;
      QTAILQ_ENTRY(CrwContainer) sibling;
@@ -180,7 +182,7 @@ static const VMStateDescription vmstate_orb = {
static bool vmstate_schdev_orb_needed(void *opaque)
  {
-    return css_migration_enabled();
+    return css_migration_enabled;
  }
static const VMStateDescription vmstate_schdev_orb = {
@@ -388,7 +390,7 @@ static int subch_dev_post_load(void *opaque, int version_id)
          css_subch_assign(s->cssid, s->ssid, s->schid, s->devno, s);
      }
- if (css_migration_enabled()) {
+    if (css_migration_enabled) {
          /* No compat voodoo to do ;) */
          return 0;
      }
@@ -412,7 +414,9 @@ static int subch_dev_post_load(void *opaque, int version_id)
void css_register_vmstate(void)
  {
-    vmstate_register(NULL, 0, &vmstate_css, &channel_subsys);
+    if (css_migration_enabled) {
+        vmstate_register(NULL, 0, &vmstate_css, &channel_subsys);
+    }
  }
IndAddr *get_indicator(hwaddr ind_addr, int len)
diff --git a/hw/s390x/s390-virtio-ccw.c b/hw/s390x/s390-virtio-ccw.c
index 1383e47eeb5..aa90703d518 100644
--- a/hw/s390x/s390-virtio-ccw.c
+++ b/hw/s390x/s390-virtio-ccw.c
@@ -275,11 +275,9 @@ static void ccw_init(MachineState *machine)
      s390_enable_css_support(s390_cpu_addr2state(0));
ret = css_create_css_image(VIRTUAL_CSSID, true);
-
      assert(ret == 0);
-    if (css_migration_enabled()) {
-        css_register_vmstate();
-    }
+
+    css_register_vmstate();
/* Create VirtIO network adapters */
      s390_create_virtio_net(BUS(css_bus), mc->default_nic);
@@ -741,7 +739,6 @@ static void ccw_machine_class_init(ObjectClass *oc, void 
*data)
s390mc->ri_allowed = true;
      s390mc->cpu_model_allowed = true;
-    s390mc->css_migration_enabled = true;
      s390mc->hpage_1m_allowed = true;
      s390mc->max_threads = 1;
      mc->init = ccw_init;
@@ -811,11 +808,6 @@ static const TypeInfo ccw_machine_info = {
      },
  };
-bool css_migration_enabled(void)
-{
-    return get_machine_class()->css_migration_enabled;
-}
-
  #define DEFINE_CCW_MACHINE(suffix, verstr, latest)                            
\
      static void ccw_machine_##suffix##_class_init(ObjectClass *oc,            
\
                                                    void *data)                 
\
@@ -1171,7 +1163,6 @@ static void ccw_machine_2_9_instance_options(MachineState 
*machine)
static void ccw_machine_2_9_class_options(MachineClass *mc)
  {
-    S390CcwMachineClass *s390mc = S390_CCW_MACHINE_CLASS(mc);
      static GlobalProperty compat[] = {
          { TYPE_S390_STATTRIB, "migration-enabled", "off", },
          { TYPE_S390_FLIC_COMMON, "migration-enabled", "off", },
@@ -1180,7 +1171,7 @@ static void ccw_machine_2_9_class_options(MachineClass 
*mc)
      ccw_machine_2_10_class_options(mc);
      compat_props_add(mc->compat_props, hw_compat_2_9, hw_compat_2_9_len);
      compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
-    s390mc->css_migration_enabled = false;
+    css_migration_enabled = false;
  }
  DEFINE_CCW_MACHINE(2_9, "2.9", false);

I think this is wrong: By adding this to ccw_machine_2_9_class_options the variable now always gets set to false, even for newer machines, since the *class_options functions are part of the "class_init" which is always done. You have to add it to ccw_machine_2_9_instance_options() instead to make it work as expected.

 Thomas


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