From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Eric Biggers <ebiggers@kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE_SIZE chunks
Date: Wed, 22 Apr 2020 13:51:11 -0600 [thread overview]
Message-ID: <CAHmME9qXy4X3GtCtt5_1+KTxTXd6+nfhvE_c8Xn6_iJdRWhQmA@mail.gmail.com> (raw)
In-Reply-To: <CAMj1kXE-UZxw0C3WRVh7RfuWE0BNDT4bt4qJa1SyOH3K-qBBcQ@mail.gmail.com>
On Wed, Apr 22, 2020 at 1:39 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Wed, 22 Apr 2020 at 09:32, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> >
> > On Tue, Apr 21, 2020 at 10:04 PM Eric Biggers <ebiggers@kernel.org> wrote:
> > > Seems this should just be a 'while' loop?
> > >
> > > while (bytes) {
> > > unsigned int todo = min_t(unsigned int, PAGE_SIZE, bytes);
> > >
> > > kernel_neon_begin();
> > > chacha_doneon(state, dst, src, todo, nrounds);
> > > kernel_neon_end();
> > >
> > > bytes -= todo;
> > > src += todo;
> > > dst += todo;
> > > }
> >
> > The for(;;) is how it's done elsewhere in the kernel (that this patch
> > doesn't touch), because then we can break out of the loop before
> > having to increment src and dst unnecessarily. Likely a pointless
> > optimization as probably the compiler can figure out how to avoid
> > that. But maybe it can't. If you have a strong preference, I can
> > reactor everything to use `while (bytes)`, but if you don't care,
> > let's keep this as-is. Opinion?
> >
>
> Since we're bikeshedding, I'd prefer 'do { } while (bytes);' here,
> given that bytes is guaranteed to be non-zero before we enter the
> loop. But in any case, I'd prefer avoiding for(;;) or while(1) where
> we can.
Okay, will do-while it up for v2.
next prev parent reply other threads:[~2020-04-22 19:51 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-20 7:57 [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE_SIZE chunks Jason A. Donenfeld
2020-04-20 8:32 ` David Laight
2020-04-21 4:02 ` Jason A. Donenfeld
2020-04-21 4:14 ` FPU register granularity [Was: Re: [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE_SIZE chunks] Jason A. Donenfeld
2020-04-21 4:25 ` Jason A. Donenfeld
2020-04-21 7:02 ` Ard Biesheuvel
2020-04-21 8:05 ` David Laight
2020-04-21 8:11 ` David Laight
2020-04-22 4:04 ` [PATCH crypto-stable] crypto: arch/lib - limit simd usage to PAGE_SIZE chunks Eric Biggers
2020-04-22 7:23 ` Ard Biesheuvel
2020-04-22 7:38 ` Jason A. Donenfeld
2020-04-22 11:28 ` Sebastian Andrzej Siewior
2020-04-22 19:35 ` Jason A. Donenfeld
2020-04-22 7:32 ` Jason A. Donenfeld
2020-04-22 7:39 ` Ard Biesheuvel
2020-04-22 19:51 ` Jason A. Donenfeld [this message]
2020-04-22 20:17 ` Jason A. Donenfeld
2020-04-23 8:45 ` Ard Biesheuvel
2020-04-22 20:03 ` [PATCH crypto-stable v2] crypto: arch - limit simd usage to 4k chunks Jason A. Donenfeld
2020-04-22 22:39 ` Eric Biggers
2020-04-22 23:09 ` Jason A. Donenfeld
2020-04-22 23:18 ` [PATCH crypto-stable v3 1/2] crypto: arch/lib " Jason A. Donenfeld
2020-04-22 23:18 ` [PATCH crypto-stable v3 2/2] crypto: arch/nhpoly1305 - process in explicit " Jason A. Donenfeld
2020-04-23 20:39 ` Eric Biggers
2020-04-23 7:18 ` [PATCH crypto-stable v3 1/2] crypto: arch/lib - limit simd usage to " Ard Biesheuvel
2020-04-23 7:40 ` Christophe Leroy
2020-04-23 7:47 ` Ard Biesheuvel
2020-04-23 18:42 ` Greg KH
2020-04-23 18:47 ` Ard Biesheuvel
2020-04-23 20:23 ` Eric Biggers
2020-04-23 20:49 ` Ard Biesheuvel
2020-04-28 23:09 ` Jason A. Donenfeld
2020-04-30 5:30 ` Herbert Xu
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