arm64 crashkernel fails to boot on acpi-only machines due to ACPI regions being no longer mapped as NOMAP

[Bhupesh Sharma]

On Tue, Dec 26, 2017 at 7:58 AM, AKASHI Takahiro
<takahiro.akashi at linaro.org> wrote:
> On Tue, Dec 26, 2017 at 09:35:17AM +0800, Dave Young wrote:
>> [snip]
>> > > > Well, we may be able to change pr_warn() to pr_warn_once() here, but
>> > > > I hope that adding "numa=off" to kernel command line should also work.
>> > >
>> > > Hmm, adding "numa=off" to crashkernel bootargs works, and TBH it was
>> > > my initial thought process as well, but I am not sure if this will
>> > > cause any regressions on aarch64 systems which use crashdump feature.
>> >
>> > It should be fine since we use numa=off by default for all other arches
>> > ie. x86, ppc64 and s390. Actually disabling numa in kdump kernel can save
>> > mm component memory usage.
>> >
>>
>> Forgot to say I means in RHEL and Fedora we use numa=off for kdump..
>
> Thank you for the clarification.
> (It might be better to make numa off automatically if maxcpus == 0 (and 1?).)
>

Not sure if we can leave this to the distribution-specific kdump
scripts (as the crashkernel boot can be held up for sufficient time
and may appear stuck). The distribution scripts may be different (for
e.g. ubuntu and RHEL/fedora) across distributions and may have
different bootarg options.

So how about considering a kernel fix only which doesn't require
relying on changing the distribution-specific kdump scripts, as we
should avoid introducing a regression while trying to fix a regression
:)

Just my 2 cents.

Thanks,
Bhupesh