Re: [Qemu-devel] Re: [PATCH 5/5] RFC: distinguish warm reset from cold reset.

[Gleb Natapov]

On Tue, Aug 31, 2010 at 08:58:06AM -0500, Anthony Liguori wrote:
> On 08/31/2010 08:46 AM, Avi Kivity wrote:
> > On 08/31/2010 04:34 PM, Anthony Liguori wrote:
> >>On 08/31/2010 08:29 AM, Avi Kivity wrote:
> >>>Note, for most devices there's no difference.  x86 has INIT
> >>>and RESET, with the keyboard controller RESET signal sometimes
> >>>wired to INIT, and RAM doesn't have RESET.  Otherwise most
> >>>devices don't see a difference.
> >>
> >>Yes, that's why I'm wondering if we can just get away with using
> >>a simple reset() callback and for the handful of devices that
> >>don't do a full reset, they can just move the state unaffected
> >>by warm reset to ->init().
> >>
> >
> >This seems reasonable.
> 
> But I'm still not sure whether the reset signal can be deliver based
> on a pre-order transversal or whether a custom transversal was
> required that each bus participates in.
> 
The thing is in qemu reset of one device can affect state of other
device. Think about device that updates its interrupt line during reset
and this affects pic/ioapic/apic. Real HW does not have a problem that
we have here.

--
                        Gleb.