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SubjectRe: [v2 2/5] arm64: kdump: implement machine_crash_shutdown()
Mark,

On 05/11/2015 04:10 PM, AKASHI Takahiro wrote:
> On 04/24/2015 07:39 PM, 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?
>
> Don't know. Will remove them.
>
>> Please use #16 * N as the offset for consistency with entry.S, with 0
>> for the first N.
>
> OK.
>
>> [...]
>>
>>> +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.
>>
>> Is there any reason we can't get the GIC driver to nuke all of this at
>> probe time?
>
> I don't get the point. You mean that the code be put in probe() of GIC driver?
> To be honest, this function was copied from arm's implementation.

Could you please elaborate a bit more details so that I can address the issue?

Thanks,
-Takahiro AKASHI

>> [...]
>>
>>> @@ -542,7 +543,7 @@ static DEFINE_RAW_SPINLOCK(stop_lock);
>>> /*
>>> * ipi_cpu_stop - handle IPI from smp_send_stop()
>>> */
>>> -static void ipi_cpu_stop(unsigned int cpu)
>>> +static void ipi_cpu_stop(unsigned int cpu, struct pt_regs *regs)
>>> {
>>> if (system_state == SYSTEM_BOOTING ||
>>> system_state == SYSTEM_RUNNING) {
>>> @@ -556,6 +557,13 @@ static void ipi_cpu_stop(unsigned int cpu)
>>>
>>> local_irq_disable();
>>>
>>> +#ifdef CONFIG_KEXEC
>>> + if (in_crash_kexec) {
>>> + crash_save_cpu(regs, cpu);
>>> + flush_cache_all();
>>
>> Any cache maintenance will need to be by VA; flush_cache_all doesn't do
>> what the name implies, though may appear to work by chance.
>>
>> Is kdump implemented for ARM? I don't see equivalent for in the arch/arm
>> ipi_cpu_stop.
>
> Arm has a dedicated function in arch/arm/kernel/machine_kexec.c:
> machine_crash_shutdown()
> => machine_crash_nonpanic_core()
>
> Thanks,
> -Takahiro AKASHI
>
>> Mark.
>>


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