linux-kernel - Re: [patch V4 part 4 15/24] x86/db: Split out dr6/7 handling

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Date:   Thu, 14 May 2020 22:37:29 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [patch V4 part 4 15/24] x86/db: Split out dr6/7 handling

On Tue, May 5, 2020 at 7:16 AM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> From: Peter Zijlstra <peterz@...radead.org>
>
> DR6/7 should be handled before nmi_enter() is invoked and restore after
> nmi_exit() to minimize the exposure.
>
> Split it out into helper inlines and bring it into the correct order.

> +        *
> +        * Entry text is excluded for HW_BP_X and cpu_entry_area, which
> +        * includes the entry stack is excluded for everything.
> +        */
> +       get_debugreg(*dr7, 6);
> +       set_debugreg(0, 7);

Fortunately, PeterZ is hiding in a brown paper bag, so I don't have to
comment :)

Other than that:

Acked-by: Andy Lutomirski <luto@...nel.org>