From: Dave Hansen <dave.hansen@intel.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: linux-crypto@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Andy Lutomirski <luto@kernel.org>,
"Chang S . Bae" <chang.seok.bae@intel.com>
Subject: Re: [PATCH v2 6/6] crypto: x86/aes-xts - wire up VAES + AVX10/512 implementation
Date: Thu, 4 Apr 2024 16:53:12 -0700 [thread overview]
Message-ID: <c806bffe-6e87-4c51-ac99-4b2612d3c334@intel.com> (raw)
In-Reply-To: <20240404233600.GA746@quark.localdomain>
On 4/4/24 16:36, Eric Biggers wrote:
> 1. Never use zmm registers.
...
> 4. Keep the proposed policy as the default behavior, but allow it to be
> overridden on the kernel command line. This would be a bit more flexible;
> however, most people don't change defaults anyway.
>
> When you write "Some folks will also surely disagree with the kernel policy
> implemented here", are there any specific concerns that you anticipate?
Some people care less about the frequency throttling and only care about
max performance _using_ AVX512.
> Note that Intel has acknowledged the zmm downclocking issues on Ice
> Lake and suggested that using ymm registers instead would be
> reasonable:>
https://lore.kernel.org/linux-crypto/e8ce1146-3952-6977-1d0e-a22758e58914@intel.com/
>
> If there is really a controversy, my vote is that for now we just go with option
> (1), i.e. drop this patch from the series. We can reconsider the issue when a
> CPU is released with better 512-bit support.
(1) is fine with me.
(4) would also be fine. But I don't think it absolutely _has_ to be a
boot-time switch. What prevents you from registering, say,
"xts-aes-vaes-avx10" and then doing:
if (avx512_is_desired())
xts-aes-vaes-avx10_512(...);
else
xts-aes-vaes-avx10_256(...);
at runtime?
Where avx512_is_desired() can be changed willy-nilly, either with a
command-line parameter or runtime knob. Sure, the performance might
change versus what was measured, but I don't think that's a deal breaker.
Then if folks want to do fancy benchmarks or model/family checks or
whatever, they can do it in userspace at runtime.
next prev parent reply other threads:[~2024-04-04 23:53 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 8:03 [PATCH v2 0/6] Faster AES-XTS on modern x86_64 CPUs Eric Biggers
2024-03-29 8:03 ` [PATCH v2 1/6] x86: add kconfig symbols for assembler VAES and VPCLMULQDQ support Eric Biggers
2024-03-29 8:03 ` [PATCH v2 2/6] crypto: x86/aes-xts - add AES-XTS assembly macro for modern CPUs Eric Biggers
2024-03-29 8:03 ` [PATCH v2 3/6] crypto: x86/aes-xts - wire up AESNI + AVX implementation Eric Biggers
2024-03-29 8:03 ` [PATCH v2 4/6] crypto: x86/aes-xts - wire up VAES + AVX2 implementation Eric Biggers
2024-03-29 8:03 ` [PATCH v2 5/6] crypto: x86/aes-xts - wire up VAES + AVX10/256 implementation Eric Biggers
2024-03-29 8:03 ` [PATCH v2 6/6] crypto: x86/aes-xts - wire up VAES + AVX10/512 implementation Eric Biggers
2024-04-04 20:34 ` Dave Hansen
2024-04-04 23:36 ` Eric Biggers
2024-04-04 23:53 ` Dave Hansen [this message]
2024-04-05 0:11 ` Eric Biggers
2024-04-05 7:20 ` Herbert Xu
2024-03-29 9:03 ` [PATCH v2 0/6] Faster AES-XTS on modern x86_64 CPUs Ard Biesheuvel
2024-03-29 9:31 ` Eric Biggers
2024-04-03 0:44 ` Eric Biggers
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