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

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Message-ID: <alpine.DEB.2.21.1803142034130.1946@nanos.tec.linutronix.de>
Date:   Wed, 14 Mar 2018 20:35:29 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Marc Zyngier <marc.zyngier@....com>
cc:     Mark Rutland <mark.rutland@....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, Marc Zyngier wrote:
> On 14/03/18 17:11, Thomas Gleixner wrote:
> > 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?
> A way to work out what is potentially missing would be to make sure that
> whatever we're removing from machine_kexec_mask_interrupts, we can find
> it in the irqchip init code. Not an easy task, and certainly not perfect
> (patches 1 and 2 in this series have no equivalent in the kexec code).
> 
> There is still another category of "reset" stuff that belongs to the
> teardown path, and that's for things that may have an impact on the
> secondary kernel.
> 
> The case I have in mind is that of the GIC LPI pending tables. These are
> allocated to the GIC, which can write pending bits at any time. Think of
> it as a DMA engine. At the moment we enter the secondary kernel, we must
> make sure the GIC has already been shut down, as the table memory will
> be reallocated.

Yes, you surely need to prevent that.

Thanks,

	tglx