dead hvc_console with kdump kernel

Milton Miller miltonm at
Thu Mar 9 03:00:14 EST 2006

On Mar 8, 2006, at 12:36 AM, Michael Ellerman wrote:

> On Mon, 6 Mar 2006 17:26, Michael Ellerman wrote:
>> On Mon, 6 Mar 2006 13:29, Michael Ellerman wrote:
>>> On Fri, 24 Feb 2006 07:41, Ryan Arnold wrote:
>>>> If interrupts end up being disabled by the kexec call and you still
>>>> need the console you could try to find a way to set hp->irq = 
>>>> NO_IRQ in
>>>> this case such that the khvcd thread is continually rescheduled to 
>>>> poll
>>>> the hypervisor buffer and never sleeps indefinitely, as via the
>>>> interrupt driven method.
>>> Still not sure what's going on here, some interrupt weirdness.
> So we take an interrupt, and while we're processing it we decide we 
> should
> panic, this happens for example if we panic via sysrq.
> The interrupt we took never gets eoi'ed, and so the second kernel will 
> never
> get another one. This is what's causing the console "hang", should have
> thought of it earlier :/ I've confirmed it happens for any irq.
> The question is how/where do we do the eoi.

On real xics it is safe to do in the initial register irq.  Don't
do it every irq register though.

Hypervisor will cover us for emulated xics if we do that.

For real mpic?  I don't know.  Maybe we do an mpic reset and that
will cover us?  Ben?


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