linux-kernel - Re: [PATCH] powerpc: ensure that swiotlb buffer is allocated from low memory

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Date:   Wed, 4 Dec 2019 14:56:32 +0100
From:   Christoph Hellwig <hch@....de>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        iommu@...ts.linux-foundation.org,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Christian Zigotzky <chzigotzky@...osoft.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Hellwig <hch@....de>,
        Darren Stevens <darren@...vens-zone.net>,
        mad skateman <madskateman@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Paul Mackerras <paulus@...ba.org>,
        Robin Murphy <robin.murphy@....com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH] powerpc: ensure that swiotlb buffer is allocated from
 low memory

On Wed, Dec 04, 2019 at 02:35:24PM +0200, Mike Rapoport wrote:
> From: Mike Rapoport <rppt@...ux.ibm.com>
> 
> Some powerpc platforms (e.g. 85xx) limit DMA-able memory way below 4G. If a
> system has more physical memory than this limit, the swiotlb buffer is not
> addressable because it is allocated from memblock using top-down mode.
> 
> Force memblock to bottom-up mode before calling swiotlb_init() to ensure
> that the swiotlb buffer is DMA-able.
> 
> Link: https://lkml.kernel.org/r/F1EBB706-73DF-430E-9020-C214EC8ED5DA@xenosoft.de
> Reported-by: Christian Zigotzky <chzigotzky@...osoft.de>
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>

Looks good:

Reviewed-by: Christoph Hellwig <hch@....de>