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Date: Mon, 10 Jul 2023 13:26:11 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Yajun Deng <yajun.deng@linux.dev>
Cc: corbet@lwn.net, hch@lst.de, m.szyprowski@samsung.com,
 robin.murphy@arm.com, paulmck@kernel.org, catalin.marinas@arm.com,
 rdunlap@infradead.org, peterz@infradead.org, rostedt@goodmis.org,
 kim.phillips@amd.com, linux-doc@vger.kernel.org,
 linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-mm@kvack.org
Subject: Re: [PATCH] dma-contiguous: support numa CMA for specified node
Message-Id: <20230710132611.ccf619f06f3ead06986cb7f4@linux-foundation.org>
In-Reply-To: <20230710074944.3501810-1-yajun.deng@linux.dev>
References: <20230710074944.3501810-1-yajun.deng@linux.dev>
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On Mon, 10 Jul 2023 15:49:44 +0800 Yajun Deng <yajun.deng@linux.dev> wrote:

> The kernel parameter 'cma_pernuma=' only supports reserving the same
> size of CMA area for each node. We need to reserve different sizes of
> CMA area for specified nodes if these devices belong to different nodes.
> 
> Change kernel parameter from 'cma_pernuma=' to 'numa_cma='. If node
> isn't specified, it will reserve CMA area for per-numa node. if the node
> is specified, it will reserve CMA area for the specified node.
> 
> At the same time, print the node id in cma_declare_contiguous_nid() if
> enabled CONFIG_NUMA.

Changing an existing kernel parameter will break existing setups.  It
would be preferable to add a new parameter for this?