linux-kernel - Re: [PATCH 0/3] irqchip: GIC kexec/kdump improvement and workarounds

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Message-ID: <alpine.DEB.2.21.1803141808350.2481@nanos.tec.linutronix.de>
Date:   Wed, 14 Mar 2018 18:11:06 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Mark Rutland <mark.rutland@....com>
cc:     Marc Zyngier <marc.zyngier@....com>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Jason Cooper <jason@...edaemon.net>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>
Subject: Re: [PATCH 0/3] irqchip: GIC kexec/kdump improvement and
 workarounds

On Wed, 14 Mar 2018, Mark Rutland wrote:
> On Tue, Mar 13, 2018 at 06:35:07PM +0000, Marc Zyngier wrote:
> > On 13/03/18 17:51, Mark Rutland wrote:
> > > On Tue, Mar 13, 2018 at 05:21:00PM +0000, Marc Zyngier wrote:
> > >> As kexec and kdump are getting used a bit more intensively, I've been
> > >> made aware of a number of shortcomings.
> > >>
> > >> The main gripe is from folks trying to launch a kdump kernel from
> > >> within an interrupt handler. If using EOImode==1, things work as
> > >> expected. If using EOImode==0 (such as in a guest), the secondary
> > >> kernel hangs as the previous interrupt hasn't been EOI'd, and the
> > >> active priority is still set. The first two patches are addressing
> > >> this situation for both GICv2 and GICv3 by reseting the APRs to their
> > >> default value.
> > > 
> > > As a more general thing, if irqchip drivers have state that needs to be
> > > reset in their init code, can we live all this irqchip reset to the
> > > crashdump kernel, and kill machine_kexec_mask_interrupts() entirely?
> > 
> > We could, once we know for sure that all the potential irqchips have
> > been fixed. Or we could just remove it immediately, and see what breaks.
> 
> I would be very tempted to do the latter.

Makes sense. Do we have any indicator that tells us that a particular irq
chip is missing something in the init code or do we have to rely on crash
reports?

Thanks,

	tglx