linux-kernel - Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update ucode on Intel's CPU

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Message-ID: <20121219232134.GA4816@jshin-Toonie>
Date:	Wed, 19 Dec 2012 17:21:34 -0600
From:	Jacob Shin <jacob.shin@....com>
To:	Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update
 ucode on Intel's CPU

On Thu, Dec 20, 2012 at 12:03:29AM +0100, Borislav Petkov wrote:
> On Wed, Dec 19, 2012 at 04:59:41PM -0600, Jacob Shin wrote:
> > I can check but right, they might be used up. But even if we had slots
> > available, the memory range that needs to be covered is in large
> > enough address and aligned in such a way that you cannot cover it with
> > variable range MTRRs.
> 
> Actually, if I'm not mistaken, you only need to cover the HT hole with
> one MTRR - the rest remains WB. And in order the mask bits to work, we
> could make it a little bigger - we waste some memory but that's nothing
> in comparison to the MCE.

Actually all memory hole above 4GB and under TOM2 needs to be marked
as UC, if the kernel just blanket calls init_memory_mapping from 4GB
to top of memory.

Right we would be loosing memory, and I think depending on the
alignment of the boundary and how many MTRRs you have avaiable to use,
significant chunks of memory could be lost. I need to go refresh on
how variable range MTRRs are programmed, it has been a while.

> 
> You might need to talk to hw guys about the feasibility of this deal
> though.
> 
> Thanks.
> 
> -- 
> Regards/Gruss,
>     Boris.
> 
> Sent from a fat crate under my desk. Formatting is fine.
> --
> 

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