linux-kernel - Re: [PATCH] x86: improve algorithm in clflush_cache

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Date:	Thu, 12 Mar 2015 20:00:26 -0600
From:	Ross Zwisler <ross.zwisler@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Dan Williams <dan.j.williams@...el.com>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH] x86: improve algorithm in clflush_cache_range

On Thu, 2015-03-12 at 12:09 +0100, Ingo Molnar wrote:
> * Ross Zwisler <ross.zwisler@...ux.intel.com> wrote:
> 
> > The current algorithm used in clflush_cache_range() can cause the last
> > cache line of the buffer to be flushed twice.
> > 
> > Fix that algorithm so that each cache line will only be flushed once,
> > and remove arithmetic on void pointers.  Void pointer arithmetic is
> > allowed by GCC extensions, but isn't part of the base C standards.
> 
> The optimization itself is fine, but that last argument is bogus: the 
> Linux kernel very much relies on 'void *' arithmetics in a gazillion 
> places.

Okay.  Are you happy with the patch as is or would you like me to
resubmit with that bit omitted from the change log?

- Ross

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