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Date:   Wed, 27 Nov 2019 09:53:51 +0100
From:   Christoph Hellwig <hch@lst.de>
To:     Mike Rapoport <rppt@linux.ibm.com>
Cc:     Christoph Hellwig <hch@lst.de>,
        Christian Zigotzky <chzigotzky@xenosoft.de>,
        Robin Murphy <robin.murphy@arm.com>,
        linux-arch@vger.kernel.org, darren@stevens-zone.net,
        mad skateman <madskateman@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        iommu@lists.linux-foundation.org, Rob Herring <robh+dt@kernel.org>,
        paulus@samba.org, rtd2@xtra.co.nz,
        "contact@a-eon.com" <contact@a-eon.com>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
        nsaenzjulienne@suse.de
Subject: Re: Bug 205201 - Booting halts if Dawicontrol DC-2976 UW SCSI
 board installed, unless RAM size limited to 3500M
Message-ID: <20191127085351.GA24676@lst.de>
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On Wed, Nov 27, 2019 at 08:56:25AM +0200, Mike Rapoport wrote:
> Maybe we'll simply force bottom up allocation before calling
> swiotlb_init()? Anyway, it's the last memblock allocation.

That should work, but I don't think it is the proper fix.  The underlying
issue here is that ZONE_DMA/DMA32 sizing is something that needs to
be propagated to memblock and dma-direct as is based around addressing
limitations.  But our zone initialization is such a mess that we
can't just reuse a variable.  Nicolas has started to clean some of
this up, but we need to clean that whole zone initialization mess up
a lot more.