linux-kernel - RE: [PATCH v7 11/13] arch/x86: Introduce QOS feature for AMD

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Date:   Tue, 13 Nov 2018 21:49:40 +0000
From:   "Yu, Fenghua" <fenghua.yu@...el.com>
To:     "Moger, Babu" <Babu.Moger@....com>,
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        "Yu, Fenghua" <fenghua.yu@...el.com>
Subject: RE: [PATCH v7 11/13] arch/x86: Introduce QOS feature for AMD

> From: Moger, Babu [mailto:Babu.Moger@....com]
> Subject: [PATCH v7 11/13] arch/x86: Introduce QOS feature for AMD
> The specification for this feature is available at
> https://developer.amd.com/wp-content/resources/56375.pdf

> +bool cbm_validate_amd(char *buf, u32 *data, struct rdt_resource *r) {
> +	if (val > r->default_ctrl) {
> +		rdt_last_cmd_puts("mask out of range\n");
> +		return false;
> +	}

If val is zero, then this closid cannot allocate any cache line.

I'm wondering: does that mean the tasks running with this closid directly access memory without cache? Is there any usage for this situation?

Thanks.

-Fenghua