qemu-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [PATCH v2 0/7] APIC/IOAPIC cleanup


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH v2 0/7] APIC/IOAPIC cleanup
Date: Mon, 23 Aug 2010 09:26:38 -0500
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.11) Gecko/20100713 Lightning/1.0b1 Thunderbird/3.0.6

On 08/23/2010 09:00 AM, Avi Kivity wrote:
 On 08/23/2010 04:48 PM, Anthony Liguori wrote:
The fundamental issue is: every function (minus trivial ones) in the device models code should have a state reference. That state reference should inherit from a DeviceState. If this statement isn't true, then the device has been modelled in qdev incorrectly.

Using this test, quite a lot of the "converted" devices are being modelled incorrectly.

Is a "state reference" allowed to have a pointer to the state, or reach it in some other way (for example, static storage for singleton devices)?


No. If this was C++, then the statement would be: device have to be implemented in terms of objects that inherit from Device. Device is our common base object.

so,

    struct MyDevicestate {
        struct DeviceState device_state;
        bool *some_bit;
    };

bad, while

    struct MyDevicestate {
        struct DeviceState device_state;
        bool some_bit;
    };

good?

And the next logical question is whether:

struct MyDeviceState {
   DeviceState qdev;
   OtherState *s;
};

Is bad? The answer would depend on whether OtherState implemented methods or not. If OtherState has no methods, it's fine. If it has methods, it's bad.




Isn't "save/restore works" an equivalent statement to "device state is reachable from the DeviceState"?

I'm not sure I can connect the dots here as I'm not sure what follows if your assertion is true.

If save/restore works then all state is reachable from one point? Presumable DeviceState?

I really don't see why the state has to be in the DeviceState subclass. We're probably talking past each other here due to some confusion in terms.

Probably. Let's say that 'structs' are containers of primatives that have no methods associated with them. 'objects' are structs that have methods and potentially constructors/destructors.

Devices can contain references to structs and objects. If a Device contains a reference to an object, the object should be stored in a BusState which is a container of Devices. Therefore, the object should inherit from Device.

Regards,

Anthony Liguori





reply via email to

[Prev in Thread] Current Thread [Next in Thread]