From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Tue, 9 Jan 2018 13:42:53 +0900 Subject: arm64 crashkernel fails to boot on acpi-only machines due to ACPI regions being no longer mapped as NOMAP In-Reply-To: References: <20171222083308.cy3vwlyhig22q5ee@fireball> <20171225032500.GA8877@linaro.org> <20171226013217.GA2119@dhcp-128-65.nay.redhat.com> <20171226013517.GA2186@dhcp-128-65.nay.redhat.com> <20171226022807.GB8877@linaro.org> Message-ID: <20180109030717.GA18820@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Bhupesh, On Tue, Jan 09, 2018 at 01:30:07AM +0530, Bhupesh Sharma wrote: > Hello Akashi, > > On Tue, Dec 26, 2017 at 8:26 AM, Bhupesh Sharma wrote: > > On Tue, Dec 26, 2017 at 7:58 AM, AKASHI Takahiro > > 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. > > > > Sorry for the delay but I was on holidays in the last week. > > Are you planning to send a patch to fix this issue or do you want me > to send a RFC version instead? I should have submitted my own patch before my new year holidays, but I will do so as soon as possible. Thanks, -Takahiro AKASHI > i think this is a blocking issue for aarch64 kdump support on newer > kernels (v4.14) and we are already hearing about this issue from other > users as well, so it would be great to get this fixed now that we have > root-caused the issue and found a possible way around. > > Regards, > Bhupesh