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From: "Philippe Mathieu-Daudé" <philmd@redhat.com>
To: qemu-devel <qemu-devel@nongnu.org>,
	Like Xu <like.xu@linux.intel.com>,
	Eduardo Habkost <ehabkost@redhat.com>
Cc: Peter Maydell <peter.maydell@linaro.org>,
	Igor Mammedov <imammedo@redhat.com>,
	"Daniel P . Berrange" <berrange@redhat.com>,
	Markus Armbruster <armbru@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>
Subject: Difference between 'current_machine' vs MACHINE(qdev_get_machine())
Date: Thu, 9 Jan 2020 12:23:01 +0100	[thread overview]
Message-ID: <a88f7647-c061-bf3f-a272-72700078ef26@redhat.com> (raw)

Hi,

"hw/boards.h" declare current_machine, and vl.c defines it:

     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?

Thanks,

Phil.



             reply	other threads:[~2020-01-09 11:23 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-09 11:23 Philippe Mathieu-Daudé [this message]
2020-01-09 12:01 ` Difference between 'current_machine' vs MACHINE(qdev_get_machine()) Paolo Bonzini
2020-01-09 15:24   ` Like Xu
2020-01-10 10:15     ` Philippe Mathieu-Daudé
2020-01-13 15:56   ` Markus Armbruster

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