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

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Message-ID: <20150312110950.GA8475@gmail.com>
Date:	Thu, 12 Mar 2015 12:09:51 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Ross Zwisler <ross.zwisler@...ux.intel.com>
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


* 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.


Thanks,

	Ingo
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