Re: [PATCH 2/2] ARM: soft-reboot into same mode that we entered the kernel

Russell King - ARM Linux
2016-12-14T12:28:51Z

On Wed, Dec 14, 2016 at 12:17:47PM +0000, Mark Rutland wrote:
> On Wed, Dec 14, 2016 at 12:05:41PM +0000, Russell King - ARM Linux wrote:
> > The issue here is that a panic can happen at any time from any context
> > with any hyp stub in place, so there _needs_ to be a uniform way to do
> > this. It's very bad that we've got this far without this point having
> > been considered - all we can do right now is to try and fix the issues
> > as they come up.
> >
> > Right now, let's fix this so we get some kind of improvement, and later
> > try to sort out some kind of uniform interface for this task.
>
> Sure, that's a bigger task, and this is definitely a step in the right
> direction.
>
> We need to avoid the kdump regression somehow though; can we somehow
> detect if KVM is active and avoid issuing the HVC_SOFT_RESTART?

That's a question for KVM people.

However, there's a bigger question, which is: what do we want to happen
in the case of kdump - do we want to be entering the kdump kernel in
HYP or SVC mode? As the kdump kernel exists to be able to save the
state of a crashing system, the kdump kernel should do that and then
restart the system in a clean way (iow, not via yet another kexec.)

So maybe the right answer is that kdump should always invoke the kernel
in SVC mode.

--
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