linux-kernel - Re: Is there anyway to do direct mapped cache on Intel hardware?

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Message-ID: <555A307B.1030300@gentoo.org>
Date:	Mon, 18 May 2015 14:33:31 -0400
From:	Richard Yao <ryao@...too.org>
To:	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Is there anyway to do direct mapped cache on Intel hardware?

It seems that there are ways:

"These are officially undocumented modes known as "cache-as-RAM mode" in
AMD land an "no-fill mode" in Intel's"
https://stackoverflow.com/questions/19591500/how-to-make-sure-a-piece-of-code-never-leaves-the-cpu-cache-l3/24710093#24710093

Now all I need to do is take time during my weekend to figure out how to
do it. My apologies for the noise.

On 05/18/2015 02:07 PM, Richard Yao wrote:
> Is there anyway to do direct mapped cache on Intel hardware?
> 
> Direct mapped cache should allow me to implement software ECC via the
> low memory / high memory split. It would be slow, but I would prefer to
> have a slow laptop than one that is vulnerable to bit flips.
> 
> If direct mapped cache is possible and non-NUMA systems could avoid
> writing it back/through, I imagine that people could also protect
> against cold boot attacks by encrypting main memory. This would be also
> be slow, but the AES instructions that Intel's newer processors are
> supposed to have should keep the slowdown within some reasonable bound.
> 
> There might also be applications for using external memory algorithms
> (e.g. fractal tree indexes) to speed up in-memory operations. I also am
> not sure if the difference between system memory and cache is big enough
> to make it a win, but I am sure that is not something that I would want
> to implement on my laptop in my spare time.
> 
> If someone knows a way to do direct mapped cache, please share.
> 



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