linux-kernel - Re: [PATCH] crypto: caam/qi - simplify CGR allocation, freeing

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Message-ID: <VI1PR0402MB3485A342A184BEBB004E74F998F70@VI1PR0402MB3485.eurprd04.prod.outlook.com>
Date:   Thu, 25 Oct 2018 14:05:32 +0000
From:   Horia Geanta <horia.geanta@....com>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Roy Pledge <roy.pledge@....com>
CC:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Leo Li <leoyang.li@....com>,
        Madalin-cristian Bucur <madalin.bucur@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] crypto: caam/qi - simplify CGR allocation, freeing

On 10/9/2018 8:11 PM, Sebastian Andrzej Siewior wrote:
> On 2018-10-08 14:09:37 [+0300], Horia Geantă wrote:
>> CGRs (Congestion Groups) have to be freed by the same CPU that
>> initialized them.
>> This is why currently the driver takes special measures; however, using
>> set_cpus_allowed_ptr() is incorrect - as reported by Sebastian.
>>
>> Instead of the generic solution of replacing set_cpus_allowed_ptr() with
>> work_on_cpu_safe(), we use the qman_delete_cgr_safe() QBMan API instead
>> of qman_delete_cgr() - which internally takes care of proper CGR
>> deletion.
>>
>> Link: https://lkml.kernel.org/r/20181005125443.dfhd2asqktm22ney@linutronix.de
>> Reported-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
>> Signed-off-by: Horia Geantă <horia.geanta@....com>
> 
> Oh. No more usage of set_cpus_allowed_ptr(). Wonderful. Thank you.
>  Acked-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> for that.
> 
> Now that you shifted my attention to qman_delete_cgr_safe().
> Could you please use work_on_cpu_safe() here instead
> smp_call_function_single() with preempt_disable() around it?
> 
> Now, what is the problem with the CPU limitation? Is this a HW
> limitation that you can access the registers from a certain CPU?
> 
Roy confirmed the CPU limitation should actually be removed, there is nothing in
HW requiring it.
A clean-up patch will follow.

Thanks,
Horia