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From: Andy Lutomirski <luto@amacapital.net>
Date: Mon, 4 Apr 2016 08:47:44 -0700
Message-ID: <CALCETrXcLdrLaOFWEPqRXHEnzAKy8sJG7s+jJFcpkbcAdAAheQ@mail.gmail.com>
Subject: Re: [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early
To: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        "H. Peter Anvin" <hpa@zytor.com>, Andy Lutomirski <luto@kernel.org>,
        X86 ML <x86@kernel.org>, Paolo Bonzini <pbonzini@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>, KVM list <kvm@vger.kernel.org>,
        Arjan van de Ven <arjan@linux.intel.com>,
        xen-devel <Xen-devel@lists.xen.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
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On Sun, Apr 3, 2016 at 7:10 AM, Borislav Petkov <bp@alien8.de> wrote:
> On Sun, Apr 03, 2016 at 06:55:00AM -0700, Andy Lutomirski wrote:
>> > No, please don't fail at early boot.
>> >
>> > Early boot is just about the *worst* situation to try to debug odd
>> > failures, exactly since things like printk may not be reliable, and
>> > things won't get logged etc.
>> >
>> > So particularly during early boot we should try as hard as possible
>> > not to crash - even if it means not being able to log about a problem.
>> > At least that way you have a hopefully working machine and can *maybe*
>> > debug things.
>> >
>>
>> In this regard, at least, my patch is the right approach.  Calling the
>> handler, whatever it is, is less likely to panic than refusing to call
>> it.
>
> Ok, good.
>
> But can we pretty please document this whole situation, i.e., the
> fact that we're trying really really hard not to fail early boot for
> debuggability reasons - either in the commit message or better in the
> code, for future reference. I think this is an important aspect to hold
> down.

I emailed out a followup patch to add a comment.

--Andy

>
> Thanks.
>
> --
> Regards/Gruss,
>     Boris.
>
> ECO tip #101: Trim your mails when you reply.


-- 
Andy Lutomirski
AMA Capital Management, LLC