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Date:   Fri, 20 Nov 2020 15:53:49 +0000
From:   Valentin Schneider <>
To:     James Morse <>
        Fenghua Yu <>,
        Reinette Chatre <>,
        Thomas Gleixner <>,
        Ingo Molnar <>, Borislav Petkov <>,
        "H. Peter Anvin" <>
Subject: Re: [PATCH 1/2] x86/intel_rdt: Check monitor group vs control group membership earlier

Hi James,

On 20/11/20 14:53, James Morse wrote:
> Hi Valentin,
> On 18/11/2020 18:00, Valentin Schneider wrote:
>> A task can only be moved between monitor groups if both groups belong to
>> the same control group. This is checked fairly late however: by that time
>> we already have appended a task_work() callback.
> (is that a problem? It's needed to do the kfree())
>> Check the validity of the move before getting anywhere near task_work
>> callbacks.
> This saves the kzalloc()/task_work_add() if it wasn't going to be necessary.

Right, to hopefully better point it out:

In such cases (invalid move), __rdtgroup_move_task() would trigger a
move_myself() task_work callback without updating {closid, rmid}.
Given nothing changed (barring concurrent updates), move_myself() won't do
any useful work.

The task_work_add() and associated alloc could thus be entirely avoided.

> Reviewed-by: James Morse <>


> Thanks,
> James

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