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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: "Horia Geantă" <horia.geanta@nxp.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	"David S. Miller" <davem@davemloft.net>,
	Aymen Sghaier <aymen.sghaier@nxp.com>,
	Li Yang <leoyang.li@nxp.com>, Roy Pledge <roy.pledge@nxp.com>,
	Madalin Bucur <madalin.bucur@nxp.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] crypto: caam/qi - simplify CGR allocation, freeing
Date: Tue, 9 Oct 2018 19:11:01 +0200	[thread overview]
Message-ID: <20181009171101.jk6lgdx4g5rnq7cm@linutronix.de> (raw)
In-Reply-To: <20181008110937.29198-1-horia.geanta@nxp.com>

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@linutronix.de>
> Signed-off-by: Horia Geantă <horia.geanta@nxp.com>

Oh. No more usage of set_cpus_allowed_ptr(). Wonderful. Thank you.
 Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.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?

This still fails (silently) if the CPU is missing, right? If you can't
get around it, you could block the CPU from going offline. You could
register a HP notifier
	cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, …

and the function would return -EINVAL if this is the special CPU. The
other thing would be forbid rmmod. This *could* work but if I remember
correctly, an explicit unbind can't be stopped.

Sebastian

  reply	other threads:[~2018-10-09 17:11 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-05 12:54 set_cpus_allowed_ptr() usage in FREESCALE CAAM Sebastian Andrzej Siewior
2018-10-08 11:09 ` [PATCH] crypto: caam/qi - simplify CGR allocation, freeing Horia Geantă
2018-10-09 17:11   ` Sebastian Andrzej Siewior [this message]
2018-10-25 14:05     ` Horia Geanta
2018-10-29  8:56       ` Sebastian Andrzej Siewior
2018-10-17  6:21   ` Herbert Xu

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