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From: | Gerd Hoffmann |
Subject: | Re: [Qemu-devel] Re: [PATCH v2 9/9] Add -kvm option |
Date: | Mon, 12 Oct 2009 13:58:46 +0200 |
User-agent: | Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.4pre) Gecko/20090922 Fedora/3.0-2.7.b4.fc11 Lightning/1.0pre Thunderbird/3.0b4 |
On 10/08/09 01:28, Anthony Liguori wrote:
Glauber Costa wrote:even if we have qdev on the irq controllers, one could still come up with situations in which we'd like to force the use of one device over another.Right, my assumption is that the devices will have different qdev names and therefore a user can select which one gets used. Right now, -device is just additive. I'm not sure the best way to express something like, replace this existing device with this new device. Maybe some trickery with id=. Gerd, any thoughts?
-M $machine gives you a barebone machine with all core devices which belong to it. You can't easily remove and/or replace devices. Especially not something central as the IRQ controller. But also no other core components, i.e. you wouldn't stick a piix4 ide controller into a Q35 machine. Just say 'no'.
That leaves two options: (1) create two devices, create new machines which use the kvm versions (aka -M pc-kvm). (2) make using the in-kernel kvm code a device property.I think (2) is the way to go. Especially with multiple devices having kvm support (apic, pit, more?) (1) becomes unmanageable.
Right now there is no way to set properties for devices *not* added via -device[1]. We'll need support for that anyway though (to set rtc properties for example), so we can have a apic.kvm property and switch between user/kernel implementions using it.
cheers, Gerd [1] my idea for implementing that is extending the compat property mechanism.
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