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Date: Tue, 31 Aug 2010 19:04:31 +0300
From: Avi Kivity <avi@redhat.com>
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Subject: Re: [Qemu-devel] Re: [PATCH 5/5] RFC: distinguish warm reset from
	cold reset.
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Gleb Natapov <gleb@redhat.com>, glommer@redhat.com, qemu-devel@nongnu.org, blauwirbel@gmail.com, Isaku Yamahata <yamahata@valinux.co.jp>, alex.williamson@redhat.com

  On 08/31/2010 06:00 PM, Anthony Liguori wrote:
> On 08/31/2010 09:03 AM, Avi Kivity wrote:
>> There's no such thing as a global reset.  There's a trace on the 
>> board that's called RESET that's connected to many chip's RESET input 
>> (but perhaps not all).  A PCI bus controller will likely propagate 
>> its RESET input into the PCI reset signal, however it's called.  So 
>> individual RESET traces are connected by chips, which have different 
>> conditions for asserting them.
>>
>> So yes, we need a custom traversal.  Some bus controllers will block 
>> off RESET completely, some will pass it through, some can reset the 
>> devices on their bus independently of the controller's RESET input, 
>> if it has one.
>>
>> (but I think we're drifting off into pointlessness here)
>
> That's my source of confusion.  I know hardware does a custom 
> transversal but from a functional perspective, do we care?
>
> So far, no one has answered this with, "yes, because device XX 
> propagates in a specific ordering of child a, b, c, d..." which I take 
> to mean that the answer is no.
>

I don't think there's an issue with the order of propagation, just 
whether propagation takes place or not.

I'd make all bus models explicitly propagate reset if they want to.