linux-kernel - Re: [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

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Message-ID: <CA+55aFw19X7PO2xd1PpUav1rSyCqUqWgi9+SA7TgjaWMaxexHQ@mail.gmail.com>
Date:	Sun, 3 Apr 2016 08:51:50 -0500
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	Andy Lutomirski <luto@...capital.net>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>, X86 ML <x86@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	KVM list <kvm@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	xen-devel <Xen-devel@...ts.xen.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

On Sun, Apr 3, 2016 at 3:07 AM, Borislav Petkov <bp@...en8.de> wrote:
>
> I'm wondering whether making it try to EFAULT correctly is the right
> thing to do... We're certainly more conservative if we panic and not
> allow some silently failed attempt at recovery which looks successful,
> to continue.

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.

            Linus