linux-kernel - Re: [PATCH v5 0/6] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

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Date:   Fri, 16 Feb 2018 13:16:50 -0600
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Baoquan He <bhe@...hat.com>, linux-kernel@...r.kernel.org,
        tglx@...utronix.de, x86@...nel.org, douly.fnst@...fujitsu.com,
        joro@...tes.org, uobergfe@...hat.com, prarit@...hat.com
Subject: Re: [PATCH v5 0/6] x86/apic: Fix restoring boot irq mode in reboot and kexec/kdump

Ingo Molnar <mingo@...nel.org> writes:

> * Baoquan He <bhe@...hat.com> wrote:
>
>> This is v5 post. Newly added patch 0002 includes the change
>> related to KEXEC_JUMP path. Patch 0003 only includes the
>> regression fix.
>> 
>> A regression bug was introduced in below commit.
>> commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC")
>> 
>> It caused the action to fail that we try to restore boot irq mode
>> in reboot and kexec/kdump. Details can be seen in patch 0003.
>> 
>> Warning can always be seen during kdump kernel boot on qemu/kvm
>> platform. Our customer even saw casual kdump kernel hang once in
>> ~30 attempts during stress testing of kdump on KVM machine.
>> 
>> v4->v5:
>>   Take out the change related to KEXEC_JUMP to a new patch 0002
>>   according to Eric's suggestion.
>>   Patch 0003 in this series only includes the regression fix.
>> 
>> v3->v4:
>>   Eric pointed out that in patch 0002 the change related to
>>   KEXEC_JUMP is not right.
>>   Correct it.
>> 
>>   Add Fixes tag and Cc to stable.
>
> Eric, are these patches looking good to you now?

The result of applying the patches looks good.
Barring whatever fix to header files that kbuild seems to find necessary.

I wish patches 1 2 and 4 were all the same patch.  That I think would
make reading the patches a bit easier, and make the backports clearer.
But at this point that is just me bike-shedding.

Reviewed-by: "Eric W. Biederman" <ebiederm@...ssion.com>

Eric