On 1/9/20 4:24 PM, Like Xu wrote:
On 2020/1/9 20:01, Paolo Bonzini wrote:
On 09/01/20 12:23, Philippe Mathieu-Daudé wrote:
current_machine =
MACHINE(object_new_with_class(OBJECT_CLASS(machine_class)));
object_property_add_child(object_get_root(), "machine",
OBJECT(current_machine), &error_abort);
The bigger user of 'current_machine' is the accel/KVM code.
Recently in a0628599f..cc7d44c2e0 "Replace global smp variables with
machine smp properties" we started to use MACHINE(qdev_get_machine()).
qdev_get_machine() resolves the machine in the QOM composition tree.
I am confused by this comment:
/* qdev_get_machine() can return something that's not TYPE_MACHINE
* if this is one of the user-only emulators; in that case there's
* no need to check the ignore_memory_transaction_failures board
flag.
*/
Following a0628599f..cc7d44c2e0, a5e0b33119 use 'current_machine' again.
What are the differences between both form, when should we use one or
another (or can we use a single one?). Can this break user-only mode?
I would always use MACHINE(qdev_get_machine()), espeecially outside
vl.c. Ideally, current_machine would be static within vl.c or even
unused outside the object_property_add_child() that you quote above.
Most of the times, I noticed from a quick grep, we actually want to
access the accelerator, not the machine, so we could add a
qemu_get_accelerator() wrapper that does
MACHINE(qdev_get_machine())->accelerator.
Paolo
I prefer to use MACHINE(qdev_get_machine()) wherever possible.
However, the qdev_get_machine() would return non TYPE_MACHINE object if:
- call qdev_get_machine() before we do
"object_property_add_child(object_get_root(), "machine",
OBJECT(current_machine), &error_abort);" in vl.c;
OK I'll add an assert() in case.
- or in the context with '#ifdef CONFIG_USER_ONLY';
Good to know, I can simplify further :)
