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Message-ID: <735f18df-0f63-44ba-adfc-70ead9ce9495@redhat.com>
Date: Tue, 9 Apr 2024 17:06:03 +0200
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Subject: Re: [PATCH v1 01/31] x86/resctrl: Fix allocation of cleanest CLOSID
 on platforms with no monitors
To: Reinette Chatre <reinette.chatre@intel.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>
 <8d1d39ca-60f0-47e9-a090-f630c6df19ae@intel.com>
From: David Hildenbrand <david@redhat.com>
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On 09.04.24 17:02, Reinette Chatre wrote:
> Hi David,
> 

Hi,

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

I'm planning on reviewing more; as most of resctrl is code I haven't 
really read before, I'm not able to make progress as fast as I normally 
would in core-MM ... :)

> 
> 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.

Oh, already in this series, great!

-- 
Cheers,

David / dhildenb