linux-kernel - Re: [PATCH v3 2/2] dma-pool: Only allocate from CMA when in same memory zone

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Message-ID: <20200807052116.GA584@lst.de>
Date:   Fri, 7 Aug 2020 07:21:16 +0200
From:   Christoph Hellwig <hch@....de>
To:     Nicolas Saenz Julienne <nsaenzjulienne@...e.de>
Cc:     amit.pundir@...aro.org, hch@....de, linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>, rientjes@...gle.com,
        jeremy.linton@....com, linux-rpi-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org
Subject: Re: [PATCH v3 2/2] dma-pool: Only allocate from CMA when in same
 memory zone

On Thu, Aug 06, 2020 at 08:47:55PM +0200, Nicolas Saenz Julienne wrote:
> There is no guarantee to CMA's placement, so allocating a zone specific
> atomic pool from CMA might return memory from a completely different
> memory zone. To get around this double check CMA's placement before
> allocating from it.

As the builtbot pointed out, memblock_start_of_DRAM can't be used from
non-__init code.  But lookig at it I think throwing that in
is bogus anyway, as cma_get_base returns a proper physical address
already.