linux-kernel - Re: [GIT PULL] x86/topology changes for v5.3

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Date:   Tue, 9 Jul 2019 15:00:15 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Ingo Molnar <mingo@...nel.org>, Kees Cook <keescook@...omium.org>
Cc:     Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] x86/topology changes for v5.3

On Tue, Jul 9, 2019 at 2:45 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> and I suspect it's the sensitive bit pinning. But I'll delve all the way.

Confirmed. Bisection says

873d50d58f67ef15d2777b5e7f7a5268bb1fbae2 is the first bad commit
commit 873d50d58f67ef15d2777b5e7f7a5268bb1fbae2
Author: Kees Cook <keescook@...omium.org>
Date:   Mon Jun 17 21:55:02 2019 -0700

    x86/asm: Pin sensitive CR4 bits

this is on a bog-standard Intel setup with F30, both desktop and
laptop (i9-9900k and i7-8565u respectively).

I haven't confirmed yet whether reverting just that one commit is
required, or if I need to revert the cr0 one too.

I also don't have any logs, because the boot never gets far enough. I
assume that there was a problem bringing up a non-boot CPU, and the
eventual hang ends up being due to that.

                   Linus