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

qdev_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] 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      |  3 +++
 hw/core/qdev-properties.c | 34 +++++++++++++++++++++++-----------
 2 files changed, 26 insertions(+), 11 deletions(-)

diff --git a/accel/accel-system.c b/accel/accel-system.c
index f6c947dd82..40c73ec62f 100644
--- a/accel/accel-system.c
+++ b/accel/accel-system.c
@@ -29,6 +29,8 @@
 #include "sysemu/cpus.h"
 #include "qemu/error-report.h"
 #include "accel-system.h"
+#include "qapi/error.h"
+#include "hw/qdev-properties.h"
 
 int accel_init_machine(AccelState *accel, MachineState *ms)
 {
@@ -43,6 +45,7 @@ int accel_init_machine(AccelState *accel, MachineState *ms)
         object_unref(OBJECT(accel));
     } else {
         object_set_accelerator_compat_props(acc->compat_props);
+        qdev_prop_set_globals(OBJECT(accel), &error_fatal);
     }
     return ret;
 }
diff --git a/hw/core/qdev-properties.c b/hw/core/qdev-properties.c
index 4867d7dd9e..462a8f96e0 100644
--- a/hw/core/qdev-properties.c
+++ b/hw/core/qdev-properties.c
@@ -10,6 +10,7 @@
 #include "qemu/cutils.h"
 #include "qdev-prop-internal.h"
 #include "qom/qom-qobject.h"
+#include "qemu/accel.h"
 
 void qdev_prop_set_after_realize(DeviceState *dev, const char *name,
                                   Error **errp)
@@ -894,27 +895,38 @@ int qdev_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