linux-kernel - Re: [PATCH 06/18] x86, barrier: stop speculation for failed access

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Message-ID: <CA+55aFzqb-p_Ng2nsXvFsibtNC2rH5fwrefwnwA3TTFVtzM3FA@mail.gmail.com>
Date:   Sun, 7 Jan 2018 11:47:07 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Willy Tarreau <w@....eu>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Dan Williams <dan.j.williams@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Network Development <netdev@...r.kernel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 06/18] x86, barrier: stop speculation for failed access_ok

On Sat, Jan 6, 2018 at 10:33 PM, Willy Tarreau <w@....eu> wrote:
>
> To be fair there's overreaction on both sides. The vast majority of
> users need to get a 100% safe system and will never notice  any
> difference.

There is no such thing as a "100% safe system". Never will be - unless
you make sure you have no users.

Also, people definitely *are* noticing the performance issues with the
current set of patches, and they are causing real problems. Go search
for reports of Amazon AWS slowdowns.

So this whole "security is so important that performance doesn't
matter" mindset is pure and utter garbage.

And the whole "normal people won't even notice" is pure garbage too.
Don't spread that bullshit when you see actual normal people
complaining.

Performance matters. A *LOT*.

                Linus