linux-kernel - Re: [PATCH 2/3] x86/intel_rdt: CBM overlap should also check for overlap with CDP peer

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Date:   Wed, 3 Oct 2018 09:02:27 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Reinette Chatre <reinette.chatre@...el.com>
cc:     fenghua.yu@...el.com, tony.luck@...el.com, jithu.joseph@...el.com,
        gavin.hindman@...el.com, dave.hansen@...el.com, mingo@...hat.com,
        hpa@...or.com, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] x86/intel_rdt: CBM overlap should also check for
 overlap with CDP peer

On Wed, 26 Sep 2018, Reinette Chatre wrote:
>  /**
> - * rdtgroup_cbm_overlaps - Does CBM for intended closid overlap with other
> + * _rdtgroup_cbm_overlaps - Does CBM for intended closid overlap with other
>   * @r: Resource to which domain instance @d belongs.
>   * @d: The domain instance for which @closid is being tested.
>   * @cbm: Capacity bitmask being tested.
> @@ -1049,8 +1048,8 @@ static int __attribute__((unused)) rdt_cdp_peer_get(struct rdt_resource *r,
>   *
>   * Return: false if CBM does not overlap, true if it does.
>   */
> -bool rdtgroup_cbm_overlaps(struct rdt_resource *r, struct rdt_domain *d,
> -			   u32 _cbm, int closid, bool exclusive)
> +static bool _rdtgroup_cbm_overlaps(struct rdt_resource *r, struct rdt_domain *d,
> +				   u32 _cbm, int closid, bool exclusive)

Existing issue. The documentation uses @cbm, but the argument is _cbm.

Also please make this __rdtgroup_cbm_overlaps(). Double underscores are
standing more out.

>  {
>  	unsigned long *cbm = (unsigned long *)&_cbm;
>  	unsigned long *ctrl_b;
> @@ -1087,6 +1086,44 @@ bool rdtgroup_cbm_overlaps(struct rdt_resource *r, struct rdt_domain *d,
>  	return false;
>  }
>  
> +/**
> + * rdtgroup_cbm_overlaps - Does CBM overlap with other use of hardware
> + * @r: Resource to which domain instance @d belongs.
> + * @d: The domain instance for which @closid is being tested.
> + * @cbm: Capacity bitmask being tested.
> + * @closid: Intended closid for @cbm.
> + * @exclusive: Only check if overlaps with exclusive resource groups
> + *
> + * Resources that can be allocated using a CBM can use the CBM to control
> + * the overlap of these allocations. rdtgroup_cmb_overlaps() is the test
> + * for overlap. Overlap test is not limited to the specific resource for
> + * which the CBM is intended though - when dealing with CDP resources that
> + * share the underlying hardware the overlap check should be performed on
> + * the CDP resource sharing the hardware also.
> + *
> + * Refer to description of _rdtgroup_cbm_overlaps() for the details of the
> + * overlap test.
> + *
> + * Return: true if CBM overlap detected, false if there is no overlap
> + */
> +bool rdtgroup_cbm_overlaps(struct rdt_resource *r, struct rdt_domain *d,
> +			   u32 _cbm, int closid, bool exclusive)

Ditto. And here is no reason for using _cbm.

> +{
> +	struct rdt_resource *r_cdp;
> +	struct rdt_domain *d_cdp;
> +	bool ret;
> +
> +	ret = _rdtgroup_cbm_overlaps(r, d, _cbm, closid, exclusive);
> +	if (ret)
> +		return ret;

  	if (__rdtgroup_cbm_overlaps(r, d, _cbm, closid, exclusive))
		return true;

> +
> +	if (rdt_cdp_peer_get(r, d, &r_cdp, &d_cdp) == 0)
> +		return _rdtgroup_cbm_overlaps(r_cdp, d_cdp, _cbm,
> +					      closid, exclusive);

	if (rdt_cdp_peer_get(r, d, &r_cdp, &d_cdp) < 0)
		return false;

	return __rdtgroup_cbm_overlaps(r_cpd, d_cdp, _cbm, closid, exclusive);

Makes the whole thing more obvious.

Thanks,

	tglx