linux-kernel - Re: [PATCH 4/8] x86/intel_rdt/mba: Memory b/w allocation feature detect

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Message-ID: <alpine.DEB.2.20.1701161456250.3877@nanos>
Date:   Mon, 16 Jan 2017 14:59:11 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Vikas Shivappa <vikas.shivappa@...ux.intel.com>
cc:     vikas.shivappa@...el.com, linux-kernel@...r.kernel.org,
        x86@...nel.org, hpa@...or.com, mingo@...nel.org,
        peterz@...radead.org, ravi.v.shankar@...el.com,
        tony.luck@...el.com, fenghua.yu@...el.com, h.peter.anvin@...el.com
Subject: Re: [PATCH 4/8] x86/intel_rdt/mba: Memory b/w allocation feature
 detect

On Tue, 10 Jan 2017, Vikas Shivappa wrote:

> Detect MBA feature if CPUID.(EAX=10H, ECX=0):EBX.L2[bit 3] = 1.
> Add supporting data structures to detect feature details which is done
> in later patch using CPUID with EAX=10H, ECX= 3.

So why is the $subject of this patch claiming that it provides the feature
detection?

> -/* CPUID.(EAX=10H, ECX=ResID=1).EDX */
> +/* CPUID.(EAX=10H, ECX=ResID=3).EAX */
> +union cpuid_0x10_3_eax {
> +	struct {
> +		unsigned int max_delay:12;
> +	} split;

And the point of this struct is?

> +	unsigned int full;
> +};

> +	if (boot_cpu_has(X86_FEATURE_MBA)) {
> +		ret = true;
> +	}

Pointless brackets.

Thanks,

	tglx