[PATCH v2 2/2] qom/object, accel-system: add support to Accel globals

[Daniel Henrique Barboza]

We're not honouring KVM options that are provided by any -accel option
aside from the first. In this example:

qemu-system-riscv64 -accel kvm,riscv-aia=emul (...) \
    -accel kvm,riscv-aia=hwaccel

'riscv-aia' will be set to 'emul', ignoring the last occurrence of the
option that set 'riscv-aia' to 'hwaccel'.

A failed attempt to solve this issue by setting 'merge_lists' can be
found in [1]. A different approach was suggested in [2]: enable global
properties for accelerators. This allows an user to override any accel
setting by using '-global' and we won't need to change how '-accel' opts
are handled.

This is done by calling object_prop_set_globals() in
accel_init_machine(). As done in device_post_init(), user's global
props take precedence over compat props so object_prop_set_globals() is
called after object_set_accelerator_compat_props().

object_prop_check_globals() is then changed to recognize TYPE_ACCEL
globals as valid.

Re-using the fore-mentioned example we'll be able to set
riscv-aia=hwaccel by doing the following:

qemu-system-riscv64 -accel kvm,riscv-aia=emul (...) \
    -global kvm-accel.riscv-aia=hwaccel

[1] 
20240701133038.1489043-1-dbarboza@ventanamicro.com/">https://lore.kernel.org/qemu-devel/20240701133038.1489043-1-dbarboza@ventanamicro.com/
[2] 
https://lore.kernel.org/qemu-devel/CABgObfbVJkCdpHV2uA7LGTbYEaoaizrbeG0vNo_T1ua5b=jq7Q@mail.gmail.com/

Reported-by: Andrew Jones <ajones@ventanamicro.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 accel/accel-system.c |  2 ++
 qom/object.c         | 34 +++++++++++++++++++++++-----------
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/accel/accel-system.c b/accel/accel-system.c
index f6c947dd82..8cb1eaa907 100644
--- a/accel/accel-system.c
+++ b/accel/accel-system.c
@@ -29,6 +29,7 @@
 #include "sysemu/cpus.h"
 #include "qemu/error-report.h"
 #include "accel-system.h"
+#include "qapi/error.h"
 
 int accel_init_machine(AccelState *accel, MachineState *ms)
 {
@@ -43,6 +44,7 @@ int accel_init_machine(AccelState *accel, MachineState *ms)
         object_unref(OBJECT(accel));
     } else {
         object_set_accelerator_compat_props(acc->compat_props);
+        object_prop_set_globals(OBJECT(accel), &error_fatal);
     }
     return ret;
 }
diff --git a/qom/object.c b/qom/object.c
index 60dbd00edd..8730e770e6 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -15,6 +15,7 @@
 #include "qapi/error.h"
 #include "qom/object.h"
 #include "qom/object_interfaces.h"
+#include "qemu/accel.h"
 #include "qemu/cutils.h"
 #include "qemu/memalign.h"
 #include "qapi/visitor.h"
@@ -516,27 +517,38 @@ int object_prop_check_globals(void)
 
     for (i = 0; i < global_props()->len; i++) {
         GlobalProperty *prop;
-        ObjectClass *oc;
+        ObjectClass *globalc, *oc;
         DeviceClass *dc;
 
         prop = g_ptr_array_index(global_props(), i);
         if (prop->used) {
             continue;
         }
-        oc = object_class_by_name(prop->driver);
-        oc = object_class_dynamic_cast(oc, TYPE_DEVICE);
-        if (!oc) {
-            warn_report("global %s.%s has invalid class name",
-                        prop->driver, prop->property);
-            ret = 1;
+        globalc = object_class_by_name(prop->driver);
+        oc = object_class_dynamic_cast(globalc, TYPE_DEVICE);
+        if (oc) {
+            dc = DEVICE_CLASS(oc);
+            if (!dc->hotpluggable && !prop->used) {
+                warn_report("global %s.%s=%s not used",
+                            prop->driver, prop->property, prop->value);
+                ret = 1;
+            }
             continue;
         }
-        dc = DEVICE_CLASS(oc);
-        if (!dc->hotpluggable && !prop->used) {
+
+        /*
+         * At this point is either an accelerator global that is
+         * unused or an invalid global. Both set ret = 1.
+         */
+        ret = 1;
+
+        oc = object_class_dynamic_cast(globalc, TYPE_ACCEL);
+        if (oc) {
             warn_report("global %s.%s=%s not used",
                         prop->driver, prop->property, prop->value);
-            ret = 1;
-            continue;
+        } else {
+            warn_report("global %s.%s has invalid class name",
+                        prop->driver, prop->property);
         }
     }
     return ret;
-- 
2.45.2