linux-kernel - Re: [PATCH V7 03/18] x86/pks: Add additional PKEY helper macros

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Date:   Thu, 25 Nov 2021 17:58:02 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     ira.weiny@...el.com, Dave Hansen <dave.hansen@...ux.intel.com>,
        Dan Williams <dan.j.williams@...el.com>
Cc:     Ira Weiny <ira.weiny@...el.com>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
        linux-mm@...ck.org
Subject: Re: [PATCH V7 03/18] x86/pks: Add additional PKEY helper macros

On Thu, Nov 25 2021 at 15:25, Thomas Gleixner wrote:
> On Tue, Aug 03 2021 at 21:32, ira weiny wrote:
>> @@ -200,16 +200,14 @@ __setup("init_pkru=", setup_init_pkru);
>>   */
>>  u32 update_pkey_val(u32 pk_reg, int pkey, unsigned int flags)
>>  {
>> -	int pkey_shift = pkey * PKR_BITS_PER_PKEY;
>> -
>>  	/*  Mask out old bit values */
>> -	pk_reg &= ~(((1 << PKR_BITS_PER_PKEY) - 1) << pkey_shift);
>> +	pk_reg &= ~PKR_PKEY_MASK(pkey);
>>  
>>  	/*  Or in new values */
>>  	if (flags & PKEY_DISABLE_ACCESS)
>> -		pk_reg |= PKR_AD_BIT << pkey_shift;
>> +		pk_reg |= PKR_AD_KEY(pkey);
>>  	if (flags & PKEY_DISABLE_WRITE)
>> -		pk_reg |= PKR_WD_BIT << pkey_shift;
>> +		pk_reg |= PKR_WD_KEY(pkey);
>
> I'm not seeing how this is improving that code. Quite the contrary.

Aside of that why are you ordering it the wrong way around, i.e.

   1) implement turd
   2) polish turd

instead of implementing the required helpers first if they are really
providing value.

Thanks,

        tglx