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SubjectRe: [v2 2/5] arm64: kdump: implement machine_crash_shutdown()
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@linaro.org>
>>> ---
>>> 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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