[PATCH v3 1/1] hw/s390x: modularize virtio-gpu-ccw

[Halil Pasic]

Since the virtio-gpu-ccw device depends on the hw-display-virtio-gpu
module, which provides the type virtio-gpu-device, packaging the
hw-display-virtio-gpu module as a separate package that may or may not
be installed along with the qemu package leads to problems. Namely if
the hw-display-virtio-gpu is absent, qemu continues to advertise
virtio-gpu-ccw, but it aborts not only when one attempts using
virtio-gpu-ccw, but also when libvirtd's capability probing tries
to instantiate the type to introspect it.

Let us thus introduce a module named hw-s390x-virtio-gpu-ccw that
is going to provide the virtio-gpu-ccw device. The hw-s390x prefix
was chosen because it is not a portable device. Because registering
virtio-gpu-ccw would make non-s390x emulator fail due to a missing
parent type, if built as a module, before registering it, we check
if the ancestor types are already registered.

With virtio-gpu-ccw built as a module, the correct way to package a
modularized qemu is to require that hw-display-virtio-gpu must be
installed whenever the module hw-s390x-virtio-gpu-ccw.

The definition S390_ADAPTER_SUPPRESSIBLE was moved to "cpu.h", per
suggestion of Thomas Huth. From interface design perspective, IMHO, not
a good thing as it belongs to the public interface of
css_register_io_adapters(). We did this because CONFIG_KVM requeires
NEED_CPU_H and Thomas, and other commenters did not like the
consequences of that.

Moving the interrupt related declarations to s390_flic.h was suggested
by Cornelia Huck.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
---

As explained in [1] the previous idea of type_register_mayfail() does
not work. The next best thing is to check if all types we need are
already registered before registering virtio-gpu-ccw from the module. It
is reasonable to assume that when the module is loaded, the ancestors
are already registered (which is not the case if the device is a
built in one).

The alternatives to this approch I could identify are:
* A poor mans version of this which checks for the parent
* Emulator specific modules:
  * An emulator specific directory within the modules directory which
    is ignored by the other emulators.
  * A way to tell the shared util library the name of this directory,
    and the code to check it if set.
  * Build hw-s390x-virtio-gpu-ccw so it lands in this special directory
    in the build tree, and install it there as well.
  I've spend some time with looking into this, but I came to the
  conclusion that the two latter points look hairy.

[1] 
https://lore.kernel.org/qemu-devel/20210222125548.346166-1-pasic@linux.ibm.com/T/#maf0608df5479f87b23606f01f732740d2617b458
---
 hw/s390x/meson.build         |  7 ++++-
 hw/s390x/virtio-ccw-gpu.c    |  5 ++++
 include/hw/s390x/css.h       |  7 -----
 include/hw/s390x/s390_flic.h |  3 +++
 include/qom/object.h         | 10 ++++++++
 qom/object.c                 | 50 ++++++++++++++++++++++++++++++++++++
 target/s390x/cpu.h           |  9 ++++---
 util/module.c                |  1 +
 8 files changed, 81 insertions(+), 11 deletions(-)

diff --git a/hw/s390x/meson.build b/hw/s390x/meson.build
index 2a7818d94b..7ac972afcf 100644
--- a/hw/s390x/meson.build
+++ b/hw/s390x/meson.build
@@ -34,7 +34,6 @@ virtio_ss.add(files('virtio-ccw.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_BALLOON', if_true: 
files('virtio-ccw-balloon.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_BLK', if_true: files('virtio-ccw-blk.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_CRYPTO', if_true: 
files('virtio-ccw-crypto.c'))
-virtio_ss.add(when: 'CONFIG_VIRTIO_GPU', if_true: files('virtio-ccw-gpu.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_INPUT', if_true: 
files('virtio-ccw-input.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio-ccw-net.c'))
 virtio_ss.add(when: 'CONFIG_VIRTIO_RNG', if_true: files('virtio-ccw-rng.c'))
@@ -46,3 +45,9 @@ virtio_ss.add(when: 'CONFIG_VHOST_USER_FS', if_true: 
files('vhost-user-fs-ccw.c'
 s390x_ss.add_all(when: 'CONFIG_VIRTIO_CCW', if_true: virtio_ss)
 
 hw_arch += {'s390x': s390x_ss}
+
+hw_s390x_modules = {}
+virtio_gpu_ccw_ss = ss.source_set()
+virtio_gpu_ccw_ss.add(when: 'CONFIG_VIRTIO_GPU', if_true: 
[files('virtio-ccw-gpu.c'), pixman])
+hw_s390x_modules += {'virtio-gpu-ccw': virtio_gpu_ccw_ss}
+modules += {'hw-s390x': hw_s390x_modules}
diff --git a/hw/s390x/virtio-ccw-gpu.c b/hw/s390x/virtio-ccw-gpu.c
index c301e2586b..ccdf6ac20f 100644
--- a/hw/s390x/virtio-ccw-gpu.c
+++ b/hw/s390x/virtio-ccw-gpu.c
@@ -62,6 +62,11 @@ static const TypeInfo virtio_ccw_gpu = {
 
 static void virtio_ccw_gpu_register(void)
 {
+#ifdef CONFIG_MODULES
+    if (!type_ancestors_registered(&virtio_ccw_gpu)) {
+        return;
+    }
+#endif
     type_register_static(&virtio_ccw_gpu);
 }
 
diff --git a/include/hw/s390x/css.h b/include/hw/s390x/css.h
index 08c869ab0a..7858666307 100644
--- a/include/hw/s390x/css.h
+++ b/include/hw/s390x/css.h
@@ -12,7 +12,6 @@
 #ifndef CSS_H
 #define CSS_H
 
-#include "cpu.h"
 #include "hw/s390x/adapter.h"
 #include "hw/s390x/s390_flic.h"
 #include "hw/s390x/ioinst.h"
@@ -233,12 +232,6 @@ uint32_t css_get_adapter_id(CssIoAdapterType type, uint8_t 
isc);
 void css_register_io_adapters(CssIoAdapterType type, bool swap, bool maskable,
                               uint8_t flags, Error **errp);
 
-#ifndef CONFIG_KVM
-#define S390_ADAPTER_SUPPRESSIBLE 0x01
-#else
-#define S390_ADAPTER_SUPPRESSIBLE KVM_S390_ADAPTER_SUPPRESSIBLE
-#endif
-
 #ifndef CONFIG_USER_ONLY
 SubchDev *css_find_subch(uint8_t m, uint8_t cssid, uint8_t ssid,
                          uint16_t schid);
diff --git a/include/hw/s390x/s390_flic.h b/include/hw/s390x/s390_flic.h
index e91b15d2d6..3907a13d07 100644
--- a/include/hw/s390x/s390_flic.h
+++ b/include/hw/s390x/s390_flic.h
@@ -134,6 +134,9 @@ void s390_flic_init(void);
 S390FLICState *s390_get_flic(void);
 QEMUS390FLICState *s390_get_qemu_flic(S390FLICState *fs);
 S390FLICStateClass *s390_get_flic_class(S390FLICState *fs);
+void s390_crw_mchk(void);
+void s390_io_interrupt(uint16_t subchannel_id, uint16_t subchannel_nr,
+                       uint32_t io_int_parm, uint32_t io_int_word);
 bool ais_needed(void *opaque);
 
 #endif /* HW_S390_FLIC_H */
diff --git a/include/qom/object.h b/include/qom/object.h
index 6721cd312e..7aa996a042 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -815,6 +815,16 @@ ObjectClass *object_get_class(Object *obj);
  */
 const char *object_get_typename(const Object *obj);
 
+/**
+ * type_ancestors_registered:
+ * @info: The #TypeInfo of the type
+ *
+ * Returns: true if all the ancestor types, that is classes and interfaces this
+ * type inherits form are all already registered, false if there is an ancestor
+ * that ain't registered yet
+ */
+bool type_ancestors_registered(const TypeInfo *info);
+
 /**
  * type_register_static:
  * @info: The #TypeInfo of the new type.
diff --git a/qom/object.c b/qom/object.c
index 491823db4a..03bd9aa2ba 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -281,6 +281,56 @@ static void object_property_free(gpointer data)
     g_free(prop);
 }
 
+static TypeImpl *type_get_parent_const(const TypeImpl *ti)
+{
+    return ti->parent_type ? ti->parent_type : type_get_by_name(ti->parent);
+}
+
+
+static bool __type_ancestors_registered(const TypeImpl *ti)
+{
+    TypeImpl *parent;
+    int i;
+
+    if (!ti) {
+        return false;
+    }
+
+    if (ti->class) {
+        /* fully initialized */
+        return true;
+    }
+
+    for (i = 0; i < ti->num_interfaces; i++) {
+        if (!type_get_by_name(ti->interfaces[i].typename)) {
+            return false;
+        }
+    }
+    if (ti->parent) {
+        parent = type_get_parent_const(ti);
+        if (!parent) {
+            return false;
+        }
+        return __type_ancestors_registered(parent);
+    }
+    return true;
+}
+
+bool type_ancestors_registered(const TypeInfo *info)
+{
+    int i;
+
+    for (i = 0; info->interfaces && info->interfaces[i].type; i++) {
+        if (!type_get_by_name(info->interfaces[i].type)) {
+            return false;
+        }
+    }
+    if (info->parent) {
+        return __type_ancestors_registered(type_get_by_name(info->parent));
+    }
+    return true;
+}
+
 static void type_initialize(TypeImpl *ti)
 {
     TypeImpl *parent;
diff --git a/target/s390x/cpu.h b/target/s390x/cpu.h
index 60d434d5ed..b434b905c0 100644
--- a/target/s390x/cpu.h
+++ b/target/s390x/cpu.h
@@ -40,6 +40,12 @@
 
 #define S390_MAX_CPUS 248
 
+#ifndef CONFIG_KVM
+#define S390_ADAPTER_SUPPRESSIBLE 0x01
+#else
+#define S390_ADAPTER_SUPPRESSIBLE KVM_S390_ADAPTER_SUPPRESSIBLE
+#endif
+
 typedef struct PSW {
     uint64_t mask;
     uint64_t addr;
@@ -806,9 +812,6 @@ int cpu_s390x_signal_handler(int host_signum, void *pinfo, 
void *puc);
 
 
 /* interrupt.c */
-void s390_crw_mchk(void);
-void s390_io_interrupt(uint16_t subchannel_id, uint16_t subchannel_nr,
-                       uint32_t io_int_parm, uint32_t io_int_word);
 #define RA_IGNORED                  0
 void s390_program_interrupt(CPUS390XState *env, uint32_t code, uintptr_t ra);
 /* service interrupts are floating therefore we must not pass an cpustate */
diff --git a/util/module.c b/util/module.c
index c65060c167..cbe89fede6 100644
--- a/util/module.c
+++ b/util/module.c
@@ -304,6 +304,7 @@ static struct {
     { "virtio-gpu-pci-base",   "hw-", "display-virtio-gpu-pci" },
     { "virtio-gpu-pci",        "hw-", "display-virtio-gpu-pci" },
     { "vhost-user-gpu-pci",    "hw-", "display-virtio-gpu-pci" },
+    { "virtio-gpu-ccw",        "hw-", "s390x-virtio-gpu-ccw"   },
     { "virtio-vga-base",       "hw-", "display-virtio-vga"    },
     { "virtio-vga",            "hw-", "display-virtio-vga"    },
     { "vhost-user-vga",        "hw-", "display-virtio-vga"    },

base-commit: 1af5629673bb5c1592d993f9fb6119a62845f576
-- 
2.25.1