linux-kernel - Re: [PATCH 1/1] x86: Quark: Enable correct cache size/type reporting

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Message-ID: <542968AE.3090407@nexus-software.ie>
Date:	Mon, 29 Sep 2014 15:11:58 +0100
From:	Bryan O'Donoghue <pure.logic@...us-software.ie>
To:	Dave Jones <davej@...hat.com>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] x86: Quark: Enable correct cache size/type reporting

On 29/09/14 14:40, Dave Jones wrote:
> On Mon, Sep 29, 2014 at 03:06:12AM +0100, Bryan O'Donoghue wrote:
>   > Quark X1000 lacks cpuid(4). It has cpuid(2) but returns no cache
>   > descriptors we can work with i.e. cpuid(2) returns
>   > eax=0x00000001 ebx=0x00000000 ecx=0x00000000 edx=0x00000000
>   >
>   > Quark X1000 contains a 16k 4-way set associative unified L1 cache
>   > with 256 sets
>   >
>   > This patch emulates cpuid(4) in a similar way to other x86
>   > processors like AMDs which don't support cpuid(4). The Quark code
>   > is based on the existing AMD code.
>
> This looks like it would work, but I wonder if it would be a lot
> simpler to do something like what we do in centaur_size_cache()
> which is the other case I recall where we had to override
> the CPUs definition of cache size.

Hi Dave.

It's working alright :)

My feeling is that we'll probably end up with less changes/new code 
taking the approach of quirking.
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