linux-kernel - Re: [PATCH 5/8] x86/intel_rct/mba: Add MBA structures and initialize MBA

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Message-ID: <alpine.DEB.2.20.1701161500210.3877@nanos>
Date:   Mon, 16 Jan 2017 15:06:08 +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 5/8] x86/intel_rct/mba: Add MBA structures and initialize
 MBA

On Tue, 10 Jan 2017, Vikas Shivappa wrote:
> +static void rdt_get_mem_config(struct rdt_resource *r)
> +{
> +	union cpuid_0x10_3_eax eax;
> +	union cpuid_0x10_x_edx edx;
> +	u32 ebx, ecx;
> +
> +	cpuid_count(0x00000010, 3, &eax.full, &ebx, &ecx, &edx.full);
> +	r->num_closid = edx.split.cos_max + 1;
> +	r->max_delay = eax.split.max_delay + 1;
> +	r->no_ctrl = 0;
> +	if (ecx & MBE_IS_LINEAR)
> +		r->delay_linear = true;
> +
> +	if (r->delay_linear)
> +		r->delay_gran = MAX_MBA_THRTL - r->max_delay;

What's the point of this extra conditional?

	if (ecx & MBE_IS_LINEAR) {
		r->delay_linear = true;
		r->delay_gran = MAX_MBA_THRTL - r->max_delay;
	}	

would be too obvious and easy to understand, right?

> +static int domain_setup_ctrlval(struct rdt_resource *r, struct rdt_domain *d)
> +{
> +	int i;
> +
> +	d->ctrl_val = kmalloc_array(r->num_closid,
> +				     sizeof(*d->ctrl_val), GFP_KERNEL);
> +	if (!d->ctrl_val) {
> +		kfree(d);

Freeing memory in the error path of some other random function is just wrong.

	if (!d->ctrl_val)
		return -ENOMEM;

and deal with the fallout at the calling function.

Thanks,

	tglx