linux-kernel - Re: [PATCH V9 2/2] powerpc/nodes: Ensure enough nodes avail for operations

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Message-ID: <87h8wyy1gt.fsf@concordia.ellerman.id.au>
Date:   Wed, 23 Aug 2017 21:20:50 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Cc:     Michael Bringmann <mwb@...ux.vnet.ibm.com>,
        John Allen <jallen@...ux.vnet.ibm.com>,
        Nathan Fontenot <nfont@...ux.vnet.ibm.com>,
        9e5050e1-e0cc-0e0e-7b31-5dcb38b307f4@...ux.vnet.ibm.com
Subject: Re: [PATCH V9 2/2] powerpc/nodes: Ensure enough nodes avail for operations

Michael Bringmann <mwb@...ux.vnet.ibm.com> writes:

> To: linuxppc-dev@...ts.ozlabs.org
>
> From: Michael Bringmann <mwb@...ux.vnet.ibm.com>
>
> To: linux-kernel@...r.kernel.org
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Michael Bringmann <mwb@...ux.vnet.ibm.com>
> Cc: John Allen <jallen@...ux.vnet.ibm.com>
> Cc: Nathan Fontenot <nfont@...ux.vnet.ibm.com>
> Subject: [PATCH V9 2/2] powerpc/nodes: Ensure enough nodes avail for operations
>
> powerpc/nodes: On systems like PowerPC which allow 'hot-add' of CPU
> or memory resources, it may occur that the new resources are to be
> inserted into nodes that were not used for these resources at bootup.
> In the kernel, any node that is used must be defined and initialized
> at boot.
>
> This patch extracts the value of the lowest domain level (number of
> allocable resources) from the "rtas" device tree property
> "ibm,max-associativity-domains" to use as the maximum number of nodes
> to setup as possibly available in the system.  This new setting will
> override the instruction,

Thanks for implementing my suggestion of using "ibm,max-associativity-domains".

However I don't think it's correct to use the lowest domain level.

It's not very clearly specified in PAPR, but I think you need to treat
it like an associativity property and index into based on the
associativity reference points.

You should be able to use min_common_depth as the index.

cheers