linux-kernel - RE: [PATCH 7/7] x86/resctrl: Determine if Sub-NUMA Cluster is enabled and initialize.

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Date:   Tue, 28 Feb 2023 20:39:31 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "babu.moger@....com" <babu.moger@....com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        "Chatre, Reinette" <reinette.chatre@...el.com>,
        "Peter Newman" <peternewman@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        "x86@...nel.org" <x86@...nel.org>
CC:     Shaopeng Tan <tan.shaopeng@...itsu.com>,
        James Morse <james.morse@....com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>
Subject: RE: [PATCH 7/7] x86/resctrl: Determine if Sub-NUMA Cluster is enabled
 and initialize.

Babu wrote:
> I am thinking loud here. Have you thought of addressing this problem?
> When a new monitor group is created, new RMID is assigned. This is done by alloc_rmid. It does not know about the rmid_offset details. This will allocate the one of the free RMIDs.
> When CPUs are assigned to the group, then per cpu  pqr_state is updated. At that point, this RMID becomes default_rmid for that cpu.

Good point. This is a gap. I haven't handled assigning CPUs to resctrl groups when SNC is enabled.

I'm not sure this has a solution :-(

-Tony