linux-kernel - Re: [PATCH] x86/kexec: Add ACPI NVS region to the ident map

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Date:   Mon, 10 Jun 2019 11:07:05 +0000
From:   Junichi Nomura <j-nomura@...jp.nec.com>
To:     Borislav Petkov <bp@...en8.de>, Kairui Song <kasong@...hat.com>
CC:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Baoquan He <bhe@...hat.com>, Dave Young <dyoung@...hat.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        "Ingo Molnar" <mingo@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        the arch/x86 maintainers <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>
Subject: Re: [PATCH] x86/kexec: Add ACPI NVS region to the ident map

Hi Kairui, Boris,

On 6/10/19 7:59 PM, Borislav Petkov wrote:
> On Mon, Jun 10, 2019 at 06:18:50PM +0800, Kairui Song wrote:
>> Hi Boris, unfortunately I don't have a real machine which only have
>> the NVS region. I did fake the memmap to emulate such problem but
>> can't really promise this will fix the real case. So just declare it
>> won't break anything that is already working. And I'm asking Junichi
>> to have a try as he reported this issue on the machines he has.
> 
> Yes, this is how you should do it. First you test on a real hardware -
> if the issue is such that needs a real hardware to verify - and if it
> passes, *then* you send the patch.
> 
> If you don't have access to the box, then ask someone who has.
> 
> But for the future, please do not send untested patches in a hurry,
> hoping that they would work. This could cause more trouble than the
> little time you might save speculating it'll all go fine.

I tested the patch on such a machine on top of the current tip/master
f9818950848 ("Marge branch 'linus'") and it works fine.
Without the patch, kexec -l fails.

I had tested the version I posted here on bunch of physical machines
I had access and confirmed it didn't broke working setups:
https://lore.kernel.org/lkml/20190515051717.GA13703@jeru.linux.bs1.fc.nec.co.jp/

Since the logic in the patch seems unchanged, I'm very sure it's ok.

-- 
Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.