linux-kernel - Re: [PATCH v7 01/49] x86/resctrl: Fix allocation of cleanest CLOSID on platforms with no monitors

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Message-ID: <37c8bd95-5cc5-41f7-99a5-6e701cec80e3@nvidia.com>
Date: Thu, 6 Mar 2025 12:56:31 -0800
From: Fenghua Yu <fenghuay@...dia.com>
To: James Morse <james.morse@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Cc: Reinette Chatre <reinette.chatre@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Borislav Petkov <bp@...en8.de>, H Peter Anvin <hpa@...or.com>,
 Babu Moger <Babu.Moger@....com>, shameerali.kolothum.thodi@...wei.com,
 D Scott Phillips OS <scott@...amperecomputing.com>,
 carl@...amperecomputing.com, lcherian@...vell.com,
 bobo.shaobowang@...wei.com, tan.shaopeng@...itsu.com,
 baolin.wang@...ux.alibaba.com, Jamie Iles <quic_jiles@...cinc.com>,
 Xin Hao <xhao@...ux.alibaba.com>, peternewman@...gle.com,
 dfustini@...libre.com, amitsinght@...vell.com,
 David Hildenbrand <david@...hat.com>, Rex Nie <rex.nie@...uarmicro.com>,
 Dave Martin <dave.martin@....com>, Koba Ko <kobak@...dia.com>,
 Shanker Donthineni <sdonthineni@...dia.com>,
 Shaopeng Tan <tan.shaopeng@...fujitsu.com>, Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH v7 01/49] x86/resctrl: Fix allocation of cleanest CLOSID
 on platforms with no monitors


On 2/28/25 11:58, James Morse wrote:
> commit 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by
> searching closid_num_dirty_rmid") added logic that causes resctrl to
> search for the CLOSID with the fewest dirty cache lines when creating a
> new control group, if requested by the arch code. This depends on the
> values read from the llc_occupancy counters. The logic is applicable to
> architectures where the CLOSID effectively forms part of the monitoring
> identifier and so do not allow complete freedom to choose an unused
> monitoring identifier for a given CLOSID.
>
> 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.
>
> Fixes: 6eac36bb9eb0 ("x86/resctrl: Allocate the cleanest CLOSID by searching closid_num_dirty_rmid")
> Signed-off-by: James Morse <james.morse@....com>
> Tested-by: Carl Worth <carl@...amperecomputing.com> # arm64
> Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
> Reviewed-by: David Hildenbrand <david@...hat.com>
> Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>
> Reviewed-by: Tony Luck <tony.luck@...el.com>

Reviewed-by: Fenghua Yu <fenghuay@...dia.com>


Thanks.


-Fenghua