Re: [v2 2/5] arm64: kdump: implement machine_crash_shutdown()

[AKASHI Takahiro]

Marc, Mark

Sorry for not revisiting your comment below for a while.

On 04/24/2015 07:43 PM, Marc Zyngier wrote:
> On 24/04/15 11:39, Mark Rutland wrote:
> > On Fri, Apr 24, 2015 at 08:53:05AM +0100, AKASHI Takahiro wrote:
> > > kdump calls machine_crash_shutdown() to shut down non-boot cpus and
> > > save per-cpu general-purpose registers before restarting the crash dump
> > > kernel. See kernel_kexec().
> > > ipi_cpu_stop() is used and a bit modified to support this behavior.
> > >
> > > Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
> > > ---
> > >   arch/arm64/include/asm/kexec.h    |   34 ++++++++++++++++++++++-
> > >   arch/arm64/kernel/machine_kexec.c |   55 ++++++++++++++++++++++++++++++++++++-
> > >   arch/arm64/kernel/smp.c           |   12 ++++++--
> > >   3 files changed, 97 insertions(+), 4 deletions(-)
> > >
> > > diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h
> > > index 3530ff5..eaf3fcb 100644
> > > --- a/arch/arm64/include/asm/kexec.h
> > > +++ b/arch/arm64/include/asm/kexec.h
> > > @@ -30,6 +30,8 @@
> > >
> > >   #if !defined(__ASSEMBLY__)
> > >
> > > +extern bool in_crash_kexec;
> > > +
> > >   /**
> > >    * crash_setup_regs() - save registers for the panic kernel
> > >    *
> > > @@ -40,7 +42,37 @@
> > >   static inline void crash_setup_regs(struct pt_regs *newregs,
> > >   				    struct pt_regs *oldregs)
> > >   {
> > > -	/* Empty routine needed to avoid build errors. */
> > > +	if (oldregs) {
> > > +		memcpy(newregs, oldregs, sizeof(*newregs));
> > > +	} else {
> > > +		__asm__ __volatile__ (
> > > +			"stp	 x0,   x1, [%3]\n\t"
> >
> > Why the tabs?
> >
> > Please use #16 * N as the offset for consistency with entry.S, with 0
> > for the first N.
> >
> > [...]
> >
> > > +static void machine_kexec_mask_interrupts(void)
> > > +{
> > > +	unsigned int i;
> > > +	struct irq_desc *desc;
> > > +
> > > +	for_each_irq_desc(i, desc) {
> > > +		struct irq_chip *chip;
> > > +
> > > +		chip = irq_desc_get_chip(desc);
> > > +		if (!chip)
> > > +			continue;
> > > +
> > > +		if (chip->irq_eoi && irqd_irq_inprogress(&desc->irq_data))
> > > +			chip->irq_eoi(&desc->irq_data);
> > > +
> > > +		if (chip->irq_mask)
> > > +			chip->irq_mask(&desc->irq_data);
> > > +
> > > +		if (chip->irq_disable && !irqd_irq_disabled(&desc->irq_data))
> > > +			chip->irq_disable(&desc->irq_data);
> > > +	}
> > > +}
> >
> > I'm surprised that this isn't left to the irqchip driver init code in
> > the crash kernel. For all we know this state could be corrupt anyway.
>
> Indeed, parsing the irqdesc list is a recipe for disaster. Who knows
> which locks have been taken or simply corrupted, pointers nuked...
>
> > Is there any reason we can't get the GIC driver to nuke all of this at
> > probe time?

Is it just enough to remove kexec_mask_interrupts() and add gic_eoi_irq()
at the beginning of gic_cpu_init() in irq-gic.c and irq-gic-v3.c?

> This feels like the better option. I can cook a patch or two for that.

If you do, that will be much better :)

BTW, in arm-gic-v3.h, GICD_CTRL_ARE_NS is defined as
    (1U << 4)
but should it be 5?
(I'm referring to the page 8-415 in IHI0069A.)

Thanks,
-Takahiro AKASHI

> Thanks,
>
> 	M.
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