linux-kernel - Re: [PATCH] crypto: x86/crc32c-intel

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Date:   Tue, 15 Dec 2020 18:02:39 +0800
From:   Tony W Wang-oc <TonyWWang-oc@...oxin.com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     <herbert@...dor.apana.org.au>, <davem@...emloft.net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <x86@...nel.org>, <hpa@...or.com>, <linux-crypto@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <TimGuo-oc@...oxin.com>,
        <CooperYan@...oxin.com>, <QiyuanWang@...oxin.com>,
        <HerryYang@...oxin.com>, <CobeChen@...oxin.com>,
        <SilviaZhao@...oxin.com>
Subject: Re: [PATCH] crypto: x86/crc32c-intel - Don't match some Zhaoxin CPUs


On 15/12/2020 16:58, Peter Zijlstra wrote:
> On Mon, Dec 14, 2020 at 11:59:52AM +0800, Tony W Wang-oc wrote:
> 
> Didn't I mention something about a comment?
> 
Really sorry for this.

>>  static const struct x86_cpu_id crc32c_cpu_id[] = {
>> +	X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 0x6, X86_FEATURE_XMM4_2, 1),
>> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x1b, X86_FEATURE_XMM4_2, 1),
>> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x3b, X86_FEATURE_XMM4_2, 1),
>> +	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 0x6, X86_FEATURE_XMM4_2, 1),
>> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x1b, X86_FEATURE_XMM4_2, 1),
>> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x3b, X86_FEATURE_XMM4_2, 1),
>>  	X86_MATCH_FEATURE(X86_FEATURE_XMM4_2, NULL),
>>  	{}
> 
> Also, the above is weird in that is has the negative entries marked
> positive, and 1/NULL are inconsistent.
> 
> Something like so then?
> That's better!

> ---
> 
> diff --git a/arch/x86/crypto/crc32c-intel_glue.c b/arch/x86/crypto/crc32c-intel_glue.c
> index feccb5254c7e..f6e6669a5102 100644
> --- a/arch/x86/crypto/crc32c-intel_glue.c
> +++ b/arch/x86/crypto/crc32c-intel_glue.c
> @@ -215,14 +215,31 @@ static struct shash_alg alg = {
>  };
>  
>  static const struct x86_cpu_id crc32c_cpu_id[] = {
> -	X86_MATCH_FEATURE(X86_FEATURE_XMM4_2, NULL),
> +	/*
> +	 * Negative entries; exclude these chips from using this driver.
> +	 * They match the positive rule below, but their CRC32 instruction
> +	 * implementation is so slow, it doesn't merrit use.
Will fix the typo merrit -> merit and resend the patch.

Sincerely
Tony

> +	 */
> +	X86_MATCH_VENDOR_FAM_FEATURE(ZHAOXIN, 0x6, X86_FEATURE_XMM4_2, false),
> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x1b, X86_FEATURE_XMM4_2, false),
> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(ZHAOXIN, 0x7, 0x3b, X86_FEATURE_XMM4_2, false),
> +	X86_MATCH_VENDOR_FAM_FEATURE(CENTAUR, 0x6, X86_FEATURE_XMM4_2, false),
> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x1b, X86_FEATURE_XMM4_2, false),
> +	X86_MATCH_VENDOR_FAM_MODEL_FEATURE(CENTAUR, 0x7, 0x3b, X86_FEATURE_XMM4_2, false),
> +	/*
> +	 * Positive entry; SSE-4.2 instructions include special purpose CRC32
> +	 * instructions.
> +	 */
> +	X86_MATCH_FEATURE(X86_FEATURE_XMM4_2, true),
>  	{}
>  };
>  MODULE_DEVICE_TABLE(x86cpu, crc32c_cpu_id);
>  
>  static int __init crc32c_intel_mod_init(void)
>  {
> -	if (!x86_match_cpu(crc32c_cpu_id))
> +	const struct x86_cpu_id *m = x86_match_cpu(crc32c_cpu_id);
> +
> +	if (!m || !m->driver_data)
>  		return -ENODEV;
>  #ifdef CONFIG_X86_64
>  	if (boot_cpu_has(X86_FEATURE_PCLMULQDQ)) {
> .
>