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From: "Maciej W. Rozycki" <macro@imgtec.com>
To: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Cc: <linux-mips@linux-mips.org>, <linux-kernel@vger.kernel.org>,
	Alexey Dobriyan <adobriyan@gmail.com>,
	John Stultz <john.stultz@linaro.org>, <mguzik@redhat.com>,
	<athorlton@sgi.com>, <mhocko@suse.com>, <ebiederm@xmission.com>,
	<gorcunov@openvz.org>, <luto@kernel.org>, <cl@linux.com>,
	<serge.hallyn@ubuntu.com>, Kees Cook <keescook@chromium.org>,
	<jslaby@suse.cz>, Andrew Morton <akpm@linux-foundation.org>,
	Florian Fainelli <f.fainelli@gmail.com>, <mingo@kernel.org>,
	<alex.smith@imgtec.com>, <markos.chandras@imgtec.com>,
	Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>,
	<david.daney@cavium.com>, <zhaoxiu.zeng@gmail.com>,
	<chenhc@lemote.com>, <Zubair.Kakakhel@imgtec.com>,
	James Hogan <james.hogan@imgtec.com>,
	Paul Burton <paul.burton@imgtec.com>,
	Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [RFC] mips: Add MXU context switching support
Date: Tue, 5 Jul 2016 11:53:17 +0100	[thread overview]
Message-ID: <alpine.DEB.2.00.1607051144190.4076@tp.orcam.me.uk> (raw)
In-Reply-To: <CANc+2y7meDYJyrHbbKWGsTNwangKCLB+kWLC6bys89PSXj-TdQ@mail.gmail.com>

On Tue, 5 Jul 2016, PrasannaKumar Muralidharan wrote:

> >> +     asm volatile(".word     0x700803ee\n\t");
> >> +     tsk->thread.mxu.xr[15] = reg_val;
> >> +}
> >
> >  Not using an output operand with asms here?
> 
> I think the instruction saves the xr* register value to reg_val
> without need for output operand.

 It does, a classic `asm' is supposed to act as an optimisation barrier.  

 However since you've used an operand `asm' in `__restore_mxu' I think 
it would be good for consistency to use one here as well; it would make 
this piece of code a little bit more readable too, as you wouldn't have 
to guess that the `asm' writes to `reg_val' then.

 So I suggest that you convert `__save_mxu' to use an operand `asm' as 
well.

  Maciej

WARNING: multiple messages have this Message-ID (diff)
From: "Maciej W. Rozycki" <macro@imgtec.com>
To: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Cc: linux-mips@linux-mips.org, linux-kernel@vger.kernel.org,
	Alexey Dobriyan <adobriyan@gmail.com>,
	John Stultz <john.stultz@linaro.org>,
	mguzik@redhat.com, athorlton@sgi.com, mhocko@suse.com,
	ebiederm@xmission.com, gorcunov@openvz.org, luto@kernel.org,
	cl@linux.com, serge.hallyn@ubuntu.com,
	Kees Cook <keescook@chromium.org>,
	jslaby@suse.cz, Andrew Morton <akpm@linux-foundation.org>,
	Florian Fainelli <f.fainelli@gmail.com>,
	mingo@kernel.org, alex.smith@imgtec.com,
	markos.chandras@imgtec.com,
	Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>,
	david.daney@cavium.com, zhaoxiu.zeng@gmail.com,
	chenhc@lemote.com, Zubair.Kakakhel@imgtec.com,
	James Hogan <james.hogan@imgtec.com>,
	Paul Burton <paul.burton@imgtec.com>,
	Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [RFC] mips: Add MXU context switching support
Date: Tue, 5 Jul 2016 11:53:17 +0100	[thread overview]
Message-ID: <alpine.DEB.2.00.1607051144190.4076@tp.orcam.me.uk> (raw)
Message-ID: <20160705105317.ckUFgGKsV7mLev45D5c2jasxUeQN09oE_hOemBl_QoA@z> (raw)
In-Reply-To: <CANc+2y7meDYJyrHbbKWGsTNwangKCLB+kWLC6bys89PSXj-TdQ@mail.gmail.com>

On Tue, 5 Jul 2016, PrasannaKumar Muralidharan wrote:

> >> +     asm volatile(".word     0x700803ee\n\t");
> >> +     tsk->thread.mxu.xr[15] = reg_val;
> >> +}
> >
> >  Not using an output operand with asms here?
> 
> I think the instruction saves the xr* register value to reg_val
> without need for output operand.

 It does, a classic `asm' is supposed to act as an optimisation barrier.  

 However since you've used an operand `asm' in `__restore_mxu' I think 
it would be good for consistency to use one here as well; it would make 
this piece of code a little bit more readable too, as you wouldn't have 
to guess that the `asm' writes to `reg_val' then.

 So I suggest that you convert `__save_mxu' to use an operand `asm' as 
well.

  Maciej

  reply	other threads:[~2016-07-05 10:53 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-25 12:14 [RFC] mips: Add MXU context switching support PrasannaKumar Muralidharan
2016-07-03 13:17 ` PrasannaKumar Muralidharan
2016-07-04 21:45 ` Florian Fainelli
2016-07-05  9:47   ` PrasannaKumar Muralidharan
2016-07-04 22:30 ` Maciej W. Rozycki
2016-07-04 22:30   ` Maciej W. Rozycki
2016-07-05 10:07   ` PrasannaKumar Muralidharan
2016-07-05 10:53     ` Maciej W. Rozycki [this message]
2016-07-05 10:53       ` Maciej W. Rozycki
2016-07-05  9:34 ` Paul Burton
2016-07-05  9:34   ` Paul Burton
2016-07-05 15:21   ` PrasannaKumar Muralidharan
2016-07-05 16:17   ` Andy Lutomirski

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