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Message-ID: <742becbc-40fb-e6da-5070-39a4b4d46a39@intel.com>
Date:   Thu, 15 Jun 2023 15:05:43 -0700
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Subject: Re: [PATCH v4 05/24] x86/resctrl: Allow RMID allocation to be scoped
 by CLOSID
Content-Language: en-US
To:     James Morse <james.morse@arm.com>, <x86@kernel.org>,
        <linux-kernel@vger.kernel.org>
CC:     Fenghua Yu <fenghua.yu@intel.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        Babu Moger <Babu.Moger@amd.com>,
        <shameerali.kolothum.thodi@huawei.com>,
        D Scott Phillips OS <scott@os.amperecomputing.com>,
        <carl@os.amperecomputing.com>, <lcherian@marvell.com>,
        <bobo.shaobowang@huawei.com>, <tan.shaopeng@fujitsu.com>,
        <xingxin.hx@openanolis.org>, <baolin.wang@linux.alibaba.com>,
        Jamie Iles <quic_jiles@quicinc.com>,
        Xin Hao <xhao@linux.alibaba.com>, <peternewman@google.com>,
        <dfustini@baylibre.com>
References: <20230525180209.19497-1-james.morse@arm.com>
 <20230525180209.19497-6-james.morse@arm.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <20230525180209.19497-6-james.morse@arm.com>
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Hi James,

On 5/25/2023 11:01 AM, James Morse wrote:

> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
> index bcc25f5339c0..27e731c7de72 100644
> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
> @@ -337,24 +337,49 @@ bool has_busy_rmid(struct rdt_resource *r, struct rdt_domain *d)
>  	return find_first_bit(d->rmid_busy_llc, idx_limit) != idx_limit;
>  }
>  
> -/*
> - * As of now the RMIDs allocation is global.
> - * However we keep track of which packages the RMIDs
> - * are used to optimize the limbo list management.
> - */
> -int alloc_rmid(void)
> +static struct rmid_entry *resctrl_find_free_rmid(u32 closid)
>  {
> -	struct rmid_entry *entry;
> -
> -	lockdep_assert_held(&rdtgroup_mutex);
> +	struct rmid_entry *itr;
> +	u32 itr_idx, cmp_idx;
>  
>  	if (list_empty(&rmid_free_lru))
> -		return rmid_limbo_count ? -EBUSY : -ENOSPC;
> +		return rmid_limbo_count ? ERR_PTR(-EBUSY) : ERR_PTR(-ENOSPC);
> +
> +	list_for_each_entry(itr, &rmid_free_lru, list) {
> +		/*
> +		 * get the index of this free RMID, and the index it would need
> +		 * to be if it were used with this CLOSID.

Please start sentences with a capital letter.

> +		 * If the CLOSID is irrelevant on this architecture, these will
> +		 * always be the same meaning the compiler can reduce this loop
> +		 * to a single list_entry_first() call.
> +		 */
> +		itr_idx = resctrl_arch_rmid_idx_encode(itr->closid, itr->rmid);
> +		cmp_idx = resctrl_arch_rmid_idx_encode(closid, itr->rmid);
> +
> +		if (itr_idx == cmp_idx)
> +			return itr;
> +	}
> +
> +	return ERR_PTR(-ENOSPC);
> +}
> +

Reinette