linux-kernel - Re: [PATCH 2/4] x86/entry: Use asm_noist_exc

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Date:   Wed, 28 Apr 2021 17:30:32 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Lai Jiangshan <laijs@...ux.alibaba.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Uros Bizjak <ubizjak@...il.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Joerg Roedel <jroedel@...e.de>, Jian Cai <caij2003@...il.com>
Subject: Re: [PATCH 2/4] x86/entry: Use asm_noist_exc_nmi() for NMI in early
 booting stage

On Tue, 27 Apr 2021 07:09:47 +0800
Lai Jiangshan <jiangshanlai@...il.com> wrote:

> While the other entries for the exceptions which use Interrupt stacks can
> be also used on the kernel stack, asm_exc_nmi() can not be used on the
> kernel stack for it relies on the RSP-located "NMI executing" variable
> which expects to on a fixed location in the NMI IST stack.  When it is
> unexpectedly called from the kernel stack, the RSP-located "NMI executing"
> variable is also on the kernel stack and is "uninitialized" and can cause
> the NMI entry to run in the wrong way.

Acked-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve