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Message-ID: <8d1d39ca-60f0-47e9-a090-f630c6df19ae@intel.com>
Date: Tue, 9 Apr 2024 08:02:28 -0700
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v1 01/31] x86/resctrl: Fix allocation of cleanest CLOSID
 on platforms with no monitors
To: David Hildenbrand <david@redhat.com>, 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>, <baolin.wang@linux.alibaba.com>, Jamie Iles
	<quic_jiles@quicinc.com>, Xin Hao <xhao@linux.alibaba.com>,
	<peternewman@google.com>, <dfustini@baylibre.com>, <amitsinght@marvell.com>,
	Rex Nie <rex.nie@jaguarmicro.com>, Dave Martin <dave.martin@arm.com>
References: <20240321165106.31602-1-james.morse@arm.com>
 <20240321165106.31602-2-james.morse@arm.com>
 <1e19965c-51f2-4f7a-8d29-e40f4e54a72c@redhat.com>
Content-Language: en-US
From: Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <1e19965c-51f2-4f7a-8d29-e40f4e54a72c@redhat.com>
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Hi David,

(Thank you very much for taking a look at these)

On 4/9/2024 1:05 AM, David Hildenbrand wrote:
> On 21.03.24 17:50, James Morse wrote:
>> commit 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by
>> searching closid_num_dirty_rmid") added a Kconfig option that causes
>> resctrl to search for the CLOSID with the fewest dirty cache lines when
>> creating a new control group. This depends on the values read from the
>> llc_occupancy counters.
>>
>> This support missed that some platforms may not have these counters.
>> This causes a NULL pointer dereference when creating a new control
>> group as the array was not allocated by dom_data_init().
>>
>> As this feature isn't necessary on platforms that don't have cache
>> occupancy monitors, add this to the check that occurs when a new
>> control group is allocated.
>>
>> The existing code is not selected by any upstream platform, it makes
>> no sense to backport this patch to stable.
>>
> 
> It's weird to not see RESCTRL_RMID_DEPENDS_ON_CLOSID appear in any Kconfig file.
> I guess it will all make sense once the refactoring is done :)

This is done later in this series where patch #29, "fs/resctrl: Add boiler
plate for external resctrl code", introduces it to fs/resctrl/Kconfig.

Reinette