From: Andy Lutomirski <luto@amacapital.net>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Andrew Lutomirski <luto@kernel.org>,
"David S. Miller" <davem@davemloft.net>,
andrew@lunn.ch, Eric Biggers <ebiggers@kernel.org>,
Greg KH <gregkh@linuxfoundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Network Development <netdev@vger.kernel.org>,
Samuel Neves <sneves@dei.uc.pt>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>
Subject: Re: [PATCH net-next v3 02/17] zinc: introduce minimal cryptography library
Date: Mon, 17 Sep 2018 09:07:43 -0700 [thread overview]
Message-ID: <CALCETrWHWZibRev=hZeE1_YFjktnpV9VBN_QmvHJfakb-saRuA@mail.gmail.com> (raw)
In-Reply-To: <CAHmME9o2sB-rQo0DRh56AFe7ZLJJh+CU6Z1m5XZ4tA8vATCy1g@mail.gmail.com>
On Mon, Sep 17, 2018 at 8:32 AM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> On Mon, Sep 17, 2018 at 4:52 PM Andy Lutomirski <luto@amacapital.net> wrote:
> > I think the module organization needs to change. It needs to be possible to have chacha20 built in but AES or whatever as a module.
>
> Okay, I'll do that for v5.
>
> > I might have agreed before Spectre :(. Unfortunately, unless we do some magic, I think the code would look something like:
> >
> > if (static_branch_likely(have_simd)) arch_chacha20();
> >
> > ...where arch_chacha20 is a *pointer*. And that will generate a retpoline and run very, very slowly. (I just rewrote some of the x86 entry code to eliminate one retpoline. I got a 5% speedup on some tests according to the kbuild bot.)
>
> Actually, the way it works now benefits from the compilers inliner and
> the branch predictor. I benchmarked this without any retpoline
> slowdowns, and the branch predictor becomes correct pretty much all
> the time. We can tinker with this after the initial merge, if you
> really want, but avoiding function pointers and instead using ordinary
> branches really winds up being quite fast.
Indeed. What I'm saying is that you shouldn't refactor it this way
because it will be slow. I agree it would be conceptually nice to be
able to blacklist a chacha20_x86_64 module to disable the asm, but I
think it would be very hard to get good performance.
--Andy
next prev parent reply other threads:[~2018-09-17 16:08 UTC|newest]
Thread overview: 103+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-11 1:08 [PATCH net-next v3 00/17] WireGuard: Secure Network Tunnel Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 01/17] asm: simd context helper API Jason A. Donenfeld
2018-09-12 6:14 ` Kevin Easton
2018-09-12 18:10 ` Jason A. Donenfeld
2018-09-13 5:03 ` Kevin Easton
2018-09-13 13:52 ` Jason A. Donenfeld
2018-09-13 13:53 ` Jason A. Donenfeld
2018-09-15 19:58 ` Andy Lutomirski
2018-09-15 20:01 ` Jason A. Donenfeld
2018-09-17 13:14 ` Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 02/17] zinc: introduce minimal cryptography library Jason A. Donenfeld
2018-09-11 10:08 ` Ard Biesheuvel
2018-09-11 14:56 ` Greg Kroah-Hartman
2018-09-11 21:47 ` Eric Biggers
2018-09-11 22:02 ` Jason A. Donenfeld
2018-09-11 23:30 ` Andrew Lunn
2018-09-11 23:57 ` David Miller
2018-09-12 0:02 ` Jason A. Donenfeld
2018-09-17 4:09 ` Andy Lutomirski
2018-09-17 4:45 ` David Miller
2018-09-17 14:55 ` Andy Lutomirski
2018-09-17 14:59 ` Jason A. Donenfeld
2018-09-17 5:07 ` Jason A. Donenfeld
2018-09-17 14:53 ` Andy Lutomirski
2018-09-17 14:59 ` Jason A. Donenfeld
2018-09-17 16:24 ` Jason A. Donenfeld
2018-09-18 16:06 ` Ard Biesheuvel
2018-09-18 16:45 ` Jason A. Donenfeld
2018-09-17 5:26 ` Ard Biesheuvel
2018-09-17 14:51 ` Andy Lutomirski
2018-09-17 15:28 ` Jason A. Donenfeld
2018-09-17 16:06 ` Andy Lutomirski
2018-09-17 16:17 ` Jason A. Donenfeld
2018-09-17 15:31 ` Jason A. Donenfeld
2018-09-17 16:07 ` Andy Lutomirski [this message]
2018-09-17 16:16 ` Jason A. Donenfeld
2018-09-17 16:18 ` Andy Lutomirski
2018-09-18 0:56 ` Jason A. Donenfeld
2018-09-17 15:52 ` Jason A. Donenfeld
2018-09-18 4:21 ` Herbert Xu
2018-09-18 4:26 ` Jason A. Donenfeld
2018-09-18 18:53 ` Ard Biesheuvel
2018-09-18 20:36 ` Jason A. Donenfeld
2018-09-19 16:55 ` Ard Biesheuvel
2018-09-11 22:16 ` Andy Lutomirski
2018-09-11 22:18 ` Jason A. Donenfeld
2018-09-11 23:01 ` Andy Lutomirski
2018-09-12 0:01 ` Jason A. Donenfeld
2018-09-12 4:29 ` Jason A. Donenfeld
2018-09-11 21:22 ` Jason A. Donenfeld
2018-09-12 22:56 ` Ard Biesheuvel
2018-09-12 23:45 ` Andy Lutomirski
2018-09-13 5:41 ` Ard Biesheuvel
2018-09-13 14:32 ` Jason A. Donenfeld
2018-09-13 15:42 ` Ard Biesheuvel
2018-09-13 15:58 ` Jason A. Donenfeld
2018-09-14 6:15 ` Ard Biesheuvel
2018-09-14 9:53 ` Jason A. Donenfeld
2018-09-13 6:39 ` Milan Broz
2018-09-13 14:34 ` Jason A. Donenfeld
2018-09-13 15:26 ` Andy Lutomirski
2018-09-13 14:18 ` Jason A. Donenfeld
2018-09-13 15:07 ` Ard Biesheuvel
2018-09-13 14:15 ` Jason A. Donenfeld
2018-09-13 15:04 ` Ard Biesheuvel
2018-09-13 15:45 ` Jason A. Donenfeld
2018-09-11 22:08 ` Eric Biggers
2018-09-12 18:16 ` Jason A. Donenfeld
2018-09-12 18:19 ` Ard Biesheuvel
2018-09-12 18:34 ` Eric Biggers
2018-09-14 6:21 ` Ard Biesheuvel
2018-09-11 1:08 ` [PATCH net-next v3 03/17] zinc: ChaCha20 generic C implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 04/17] zinc: ChaCha20 ARM and ARM64 implementations Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 05/17] zinc: ChaCha20 x86_64 implementation Jason A. Donenfeld
2018-09-11 8:22 ` Thomas Gleixner
2018-09-11 9:00 ` Samuel Neves
2018-09-11 9:09 ` Thomas Gleixner
2018-09-11 21:12 ` Jason A. Donenfeld
2018-09-11 21:27 ` Thomas Gleixner
2018-09-11 21:28 ` Jason A. Donenfeld
2018-09-11 21:48 ` Eric Biggers
2018-09-11 22:04 ` Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 06/17] zinc: ChaCha20 MIPS32r2 implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 07/17] zinc: Poly1305 generic C implementation and selftest Jason A. Donenfeld
2018-09-11 1:17 ` Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 07/17] zinc: Poly1305 generic C implementations " Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 08/17] zinc: Poly1305 ARM and ARM64 implementations Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 09/17] zinc: Poly1305 x86_64 implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 10/17] zinc: Poly1305 MIPS32r2 and MIPS64 implementations Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 11/17] zinc: ChaCha20Poly1305 construction and selftest Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 12/17] zinc: BLAKE2s generic C implementation " Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 13/17] zinc: BLAKE2s x86_64 implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 14/17] zinc: Curve25519 generic C implementations and selftest Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 15/17] zinc: Curve25519 ARM implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 16/17] zinc: Curve25519 x86_64 implementation Jason A. Donenfeld
2018-09-11 1:08 ` [PATCH net-next v3 17/17] net: WireGuard secure network tunnel Jason A. Donenfeld
2018-09-11 12:59 ` kbuild test robot
2018-09-11 20:53 ` Jason A. Donenfeld
2018-09-11 13:17 ` kbuild test robot
2018-09-11 21:05 ` Jason A. Donenfeld
2018-09-11 13:30 ` Andrew Lunn
2018-09-11 21:08 ` Jason A. Donenfeld
2018-09-11 21:55 ` Andrew Lunn
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