linux-kernel - Re: [PATCH] x86: Intel Cache Allocation Technology support

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Date:	Fri, 21 Nov 2014 21:43:34 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Dave Hansen <dave.hansen@...el.com>
cc:	Vikas Shivappa <vikas.shivappa@...ux.intel.com>,
	linux-kernel@...r.kernel.org, vikas.shivappa@...el.com,
	hpa@...or.com, mingo@...nel.org, tj@...nel.org,
	matt.flemming@...el.com, will.auld@...el.com, peterz@...radead.org
Subject: Re: [PATCH] x86: Intel Cache Allocation Technology support

On Fri, 21 Nov 2014, Dave Hansen wrote:
> On 11/19/2014 05:05 PM, Vikas Shivappa wrote:
> > +	/*
> > +	 * Hard code the checks and values for HSW SKUs.
> > +	 * Unfortunately! have to check against only these brand name strings.
> > +	 */
> > +
> > +	for (i = 0; i < 5; i++)
> > +		if (!strcmp(hsw_brandstrs[i], c->x86_model_id)) {
> > +			c->x86_cqe_closs = 4;
> > +			c->x86_cqe_cbmlength = 20;
> > +			return true;
> > +		}
> 
> Please use ARRAY_SIZE() here.  Otherwise, I guarantee the next string
> you add to hsw_brandstrs[] gets silently ignored.
> 
> Are there really only 5 CPUs?  This:
> 
> > http://ark.intel.com/products/family/78583/Intel-Xeon-Processor-E5-v3-Family#@Server
> 
> lists 32 skus.

We really should find a proper software probing solution for this
instead of having a gazillion of brand strings plus micro code version
checks around for this.

Why cant the HW folks release a micro code version which fixes the
obviously wreckaged CPUID enumeration of this feature instead of
burdening us with that horror?

Can you please find a proper sized clue bat and whack your HW folks
over the head for this insanity?

Thanks,

	tglx
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