linux-kernel - Re: [RFC PATCH v2 3/6] x86/pti: add a per-cpu variable pti

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Message-ID: <20180110071951.t4vbwlnlw2qycnpm@gmail.com>
Date:   Wed, 10 Jan 2018 08:19:51 +0100
From:   Ingo Molnar <mingo@...nel.org>
To:     Willy Tarreau <w@....eu>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH v2 3/6] x86/pti: add a per-cpu variable pti_disable


* Willy Tarreau <w@....eu> wrote:

> +#ifdef CONFIG_PAGE_TABLE_ISOLATION
> +	this_cpu_write(pti_disable,
> +		       next_p->mm && next_p->mm->context.pti_disable);
> +#endif

Another pet peeve, please write:

> +	this_cpu_write(pti_disable, next_p->mm && next_p->mm->context.pti_disable);

or consider introducing an 'mm_next' local variable, set to next_p->mm, and use 
that to shorten the sequence.

More importantly, any strong reasons why the flag is logic-inverted? I.e. why not
::pti_enabled?

Thanks,

	Ingo