qemu-devel
[Top][All Lists]
Advanced

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

Re: [Qemu-devel] [PATCH 00/15] qdev: make reset semantics more clear and


From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH 00/15] qdev: make reset semantics more clear and consistent, reset qbuses under virtio devices
Date: Mon, 07 Jan 2013 14:51:17 -0600
User-agent: Notmuch/0.13.2+93~ged93d79 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu)

Peter Maydell <address@hidden> writes:

> On 7 January 2013 20:20, Anthony Liguori <address@hidden> wrote:
>> Peter Maydell <address@hidden> writes:
>>> On 7 January 2013 19:10, Anthony Liguori <address@hidden> wrote:
>>>> I think reset really ought to just be a bus level concept with
>>>> individual implementations for each bus.
>>>
>>> I'm not sure I really agree here, especially since QOM/qdev are
>>> moving away from the idea that there is a single bus tree and every
>>> device is on a single bus.
>>
>> I don't mean a BusState level concept, I mean a PCIBus concept.
>>
>> There is clearly such a thing as a PCI bus reset.  In fact, there are
>> multiple types of PCI bus resets.  There should be a PCIBus method that
>> calls out to PCIDevices on the bus.
>>
>> But that isn't something that should be fitted into generalized to a
>> BusState::reset method.
>
> Ah, I see what you mean now -- yes, definitely.
>
>>> If we want to model reset properly we should model actual reset
>>> lines (and/or power-cycling). If we don't care we can continue with
>>> whatever fudge we like :-)
>>
>> Yes, and that's basically what qemu_system_reset() is.  Of course, we
>> model it like everything is directly connected to a single power source
>> which is true 99% of the time.  That's why we've gotten away with it for
>> so long.
>
> I think the bit that's most creaky here is what you do about devices
> that want to assert outgoing irq/whatever lines immediately on
> powerup.

This isn't so much a reset problem as a consequence of stateless IRQ
lines.  If IRQ lines were stateful, this problem wouldn't exist.

And yes, I will post Pins one day...

Regards,

Anthony Liguori

>
> -- PMM




reply via email to

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