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Date:   Fri, 11 Dec 2020 09:43:57 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>
Cc:     herbert@gondor.apana.org.au, davem@davemloft.net,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org,
        hpa@zytor.com, linux-crypto@vger.kernel.org,
        linux-kernel@vger.kernel.org, TimGuo-oc@zhaoxin.com,
        CooperYan@zhaoxin.com, QiyuanWang@zhaoxin.com,
        HerryYang@zhaoxin.com, CobeChen@zhaoxin.com, SilviaZhao@zhaoxin.com
Subject: Re: [PATCH] crypto: x86/crc32c-intel - Don't match some Zhaoxin CPUs
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On Fri, Dec 11, 2020 at 07:29:04PM +0800, Tony W Wang-oc wrote:
> The driver crc32c-intel match CPUs supporting X86_FEATURE_XMM4_2.
> On platforms with Zhaoxin CPUs supporting this X86 feature, When
> crc32c-intel and crc32c-generic are both registered, system will
> use crc32c-intel because its .cra_priority is greater than
> crc32c-generic. This case expect to use crc32c-generic driver for
> some Zhaoxin CPUs to get performance gain, So remove these Zhaoxin
> CPUs support from crc32c-intel.
> 
> Signed-off-by: Tony W Wang-oc <TonyWWang-oc@zhaoxin.com>

Does this mean that the performance of the crc32c instruction on those CPUs is
actually slower than a regular C implementation?  That's very weird.

- Eric