From: Peter Zijlstra <peterz@infradead.org>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Mark Rutland <mark.rutland@arm.com>,
linux-rt-users@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
linux-kernel@vger.kernel.org,
Steven Rostedt <rostedt@goodmis.org>,
tglx@linutronix.de, linux-arm-kernel@lists.infradead.org,
ard.biesheuvel@linaro.org
Subject: Re: [PATCH RT] arm*: disable NEON in kernel mode
Date: Fri, 1 Dec 2017 18:14:58 +0100 [thread overview]
Message-ID: <20171201171458.3a2acsltiq54gvuu@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20171201143648.GK1612@linutronix.de>
On Fri, Dec 01, 2017 at 03:36:48PM +0100, Sebastian Andrzej Siewior wrote:
> On 2017-12-01 14:18:28 [+0000], Mark Rutland wrote:
> > [Adding Ard, who wrote the NEON crypto code]
> >
> > On Fri, Dec 01, 2017 at 02:45:06PM +0100, Sebastian Andrzej Siewior wrote:
> > > +arm folks, to let you know
> > >
> > > On 2017-12-01 11:43:32 [+0100], To linux-rt-users@vger.kernel.org wrote:
> > > > NEON in kernel mode is used by the crypto algorithms and raid6 code.
> > > > While the raid6 code looks okay, the crypto algorithms do not: NEON
> > > > is enabled on first invocation and may allocate/free/map memory before
> > > > the NEON mode is disabled again.
> >
> > Could you elaborate on why this is a problem?
> >
> > I guess this is because kernel_neon_{begin,end}() disable preemption?
> >
> > ... is this specific to RT?
>
> It is RT specific, yes. One thing are the unbounded latencies since
> everything in this preempt_disable section can take time depending on
> the size of the request.
Well, PREEMPT cares about that too.
next prev parent reply other threads:[~2017-12-01 17:15 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 14:22 [PATCH RT] crypto: limit more FPU-enabled sections Sebastian Andrzej Siewior
2017-11-30 14:30 ` Sebastian Andrzej Siewior
2017-12-01 10:43 ` [PATCH RT] arm*: disable NEON in kernel mode Sebastian Andrzej Siewior
2017-12-01 13:45 ` Sebastian Andrzej Siewior
2017-12-01 14:18 ` Mark Rutland
2017-12-01 14:36 ` Sebastian Andrzej Siewior
2017-12-01 15:03 ` Ard Biesheuvel
2017-12-01 17:58 ` Dave Martin
2017-12-01 18:08 ` Russell King - ARM Linux
2017-12-01 18:24 ` Dave Martin
2017-12-01 19:20 ` Ard Biesheuvel
2017-12-04 9:21 ` Sebastian Andrzej Siewior
2017-12-01 17:14 ` Peter Zijlstra [this message]
2017-12-01 17:31 ` Russell King - ARM Linux
2017-12-01 17:39 ` Peter Zijlstra
2017-11-30 15:19 ` [PATCH RT] crypto: limit more FPU-enabled sections Steven Rostedt
2017-11-30 15:22 ` Sebastian Andrzej Siewior
2017-12-01 10:44 ` [PATCH RT v2] " Sebastian Andrzej Siewior
2017-12-01 11:32 ` Peter Zijlstra
2017-12-01 13:32 ` Sebastian Andrzej Siewior
2017-12-01 13:44 ` Peter Zijlstra
2017-12-01 13:50 ` Sebastian Andrzej Siewior
2017-12-01 14:03 ` [PATCH RT v3] " Sebastian Andrzej Siewior
2017-11-30 15:29 ` [PATCH RT] " Steven Rostedt
2017-11-30 15:41 ` Sebastian Andrzej Siewior
2017-11-30 16:18 ` Steven Rostedt
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