linux-kernel - Re: [RFC PATCH] asm/generic: introduce if_nospec and nospec

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Message-ID: <20180104231137.0c09a674@alans-desktop>
Date:   Thu, 4 Jan 2018 23:11:37 +0000
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        Pavel Machek <pavel@....cz>,
        Julia Lawall <julia.lawall@...6.fr>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        linux-arch@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Elena Reshetova <elena.reshetova@...el.com>,
        Alan Cox <alan@...ux.intel.com>,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [RFC PATCH] asm/generic: introduce if_nospec and nospec_barrier

> It's also possible that x86 'lfence' really is so fast that it doesn't
> make sense to try to do this.

If you've got a lot going on it's not 1 cycle.

Alan