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Message-ID: <d93950f3-1ceb-9652-f223-f6e550f8a818@intel.com>
Date:   Wed, 9 Aug 2023 15:32:42 -0700
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Subject: Re: [PATCH v5 02/24] x86/resctrl: Access per-rmid structures by index
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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: <20230728164254.27562-1-james.morse@arm.com>
 <20230728164254.27562-3-james.morse@arm.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <20230728164254.27562-3-james.morse@arm.com>
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Hi James,

On 7/28/2023 9:42 AM, James Morse wrote:


> @@ -600,7 +600,7 @@ static void clear_closid_rmid(int cpu)
>  	state->default_rmid = 0;
>  	state->cur_closid = 0;
>  	state->cur_rmid = 0;
> -	wrmsr(MSR_IA32_PQR_ASSOC, 0, 0);
> +	wrmsr(MSR_IA32_PQR_ASSOC, 0, RESCTRL_RESERVED_CLOSID);
>  }

Can the remaining "0" be replaced with RESCTRL_RESERVED_RMID?


...

> @@ -377,14 +399,17 @@ static void add_rmid_to_limbo(struct rmid_entry *entry)
>  
>  void free_rmid(u32 closid, u32 rmid)
>  {
> +	u32 idx = resctrl_arch_rmid_idx_encode(closid, rmid);
>  	struct rmid_entry *entry;
>  
> -	if (!rmid)
> -		return;
> -
>  	lockdep_assert_held(&rdtgroup_mutex);
>  
> -	entry = __rmid_entry(closid, rmid);
> +	/* do not allow the default rmid to be free'd */
> +	if (idx == resctrl_arch_rmid_idx_encode(RESCTRL_RESERVED_CLOSID,
> +						RESCTRL_RESERVED_RMID))
> +		return;
> +

Why is this encoding necessary? Can the provided function parameters
not be tested directly against RESCTRL_RESERVED_CLOSID and
RESCTRL_RESERVED_RMID ?

> +	entry = __rmid_entry(idx);
>  
>  	if (is_llc_occupancy_enabled())
>  		add_rmid_to_limbo(entry);

Reinette