Re: [Qemu-devel] [PATCH] qdev: Reset hotplugged devices

[Avi Kivity <avi@redhat.com>]

  On 08/26/2010 04:25 PM, Anthony Liguori wrote:
> On 08/26/2010 08:15 AM, Avi Kivity wrote:
>>  On 08/25/2010 03:55 PM, Anthony Liguori wrote:
>>>
>>>> Maybe we can merge the patches.
>>>> As for your patch, I have some comment.
>>>> - bus itself may want its own handler. At lease pci bus needs it.
>>>>    And propagating reset signal to children is up to the bus 
>>>> controller.
>>>
>>> I disagree.  Reset should be equivalent to power off + init and it's 
>>> not something that can be selectively propagated.
>>
>> Not all busses propagate reset - SCSI is an example (I think).
>>
>
> We're talking about cold reset vs. warm reset.
>
> In the absence of passthrough, I'm struggling to see a useful use-case 
> with warm reset.  However, there are many useful things we can do 
> assuming a cold reset (like MADV_DONTNEED memory on reboot).
>
> That's not saying we shouldn't do a warm reset, but I'd like to see 
> that as an incremental addition to what we have today (like 
> introducing a propagating warm reset callback) and thinking through 
> what the actual behavior should and shouldn't be.

Pressing the reset button is a warm reset on real machines, therefore it 
should be a warm reset in qemu.

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