linux-kernel - Re: [PATCH v3 1/2] x86: Add support for the pcommit instruction

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Message-ID: <20150128105818.GE12929@pd.tnic>
Date:	Wed, 28 Jan 2015 11:58:18 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Ross Zwisler <ross.zwisler@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org,
	H Peter Anvin <h.peter.anvin@...el.com>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v3 1/2] x86: Add support for the pcommit instruction

On Tue, Jan 27, 2015 at 09:53:50AM -0700, Ross Zwisler wrote:
> Add support for the new pcommit (persistent commit) instruction.  This
> instruction was announced in the document "Intel Architecture
> Instruction Set Extensions Programming Reference" with reference number
> 319433-022.
> 
> https://software.intel.com/sites/default/files/managed/0d/53/319433-022.pdf
> 
> The pcommit instruction ensures that data that has been flushed from the
> processor's cache hierarchy with clwb, clflushopt or clflush is accepted to
> memory and is durable on the DIMM.  The primary use case for this is persistent
> memory.
> 
> This function shows how to properly use clwb/clflushopt/clflush and
> pcommit with appropriate fencing:

...

> This is still correct, but now you've got two fences separated by only a
> nop.  With the commit and the fence together in pcommit_sfence() you
> avoid the final unneeded fence.
> 
> Signed-off-by: Ross Zwisler <ross.zwisler@...ux.intel.com>
> Cc: H Peter Anvin <h.peter.anvin@...el.com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Borislav Petkov <bp@...en8.de>

Acked-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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