From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 12/16] staging/comedi: mark as broken
Date: Fri, 14 Jun 2019 16:48:57 +0200
Message-ID: <20190614144857.GA9088@lst.de>
References: <20190614134726.3827-1-hch@lst.de> <20190614134726.3827-13-hch@lst.de> <20190614140239.GA7234@kroah.com>
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To: Greg KH <gregkh@linuxfoundation.org>
Cc: Christoph Hellwig <hch@lst.de>, Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <maxime.ripard@bootlin.com>, Sean Paul <sean@poorly.run>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, Ian Abbott <abbotti@mev.co.uk>, H Hartley Sweeten <hsweeten@visionengravers.com>, devel@driverdev.osuosl.org, linux-s390@vger.kernel.org, Intel Linux Wireless <linuxwifi@intel.com>, linux-rdma@vger.kernel.org, netdev@vger.kernel.org, intel-gfx@lists.freedesktop.org, linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org
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On Fri, Jun 14, 2019 at 04:02:39PM +0200, Greg KH wrote:
> Perhaps a hint as to how we can fix this up?  This is the first time
> I've heard of the comedi code not handling dma properly.

It can be fixed by:

 a) never calling virt_to_page (or vmalloc_to_page for that matter)
    on dma allocation
 b) never remapping dma allocation with conflicting cache modes
    (no remapping should be doable after a) anyway).