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From: Christoph Hellwig <hch@lst.de>
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,
	"moderated list:ARM PORT" <linux-arm-kernel@lists.infradead.org>,
	linux-media@vger.kernel.org
Subject: Re: [PATCH 12/16] staging/comedi: mark as broken
Date: Fri, 14 Jun 2019 17:34:28 +0200
Message-ID: <20190614153428.GA10008@lst.de> (raw)
In-Reply-To: <20190614153032.GD18049@kroah.com>

On Fri, Jun 14, 2019 at 05:30:32PM +0200, Greg KH wrote:
> On Fri, Jun 14, 2019 at 04:48:57PM +0200, Christoph Hellwig wrote:
> > 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).
> 
> Ok, fair enough, have any pointers of drivers/core code that does this
> correctly?  I can put it on my todo list, but might take a week or so...

Just about everyone else.  They just need to remove the vmap and
either do one large allocation, or live with the fact that they need
helpers to access multiple array elements instead of one net vmap,
which most of the users already seem to do anyway, with just a few
using the vmap (which might explain why we didn't see blowups yet).

  reply index

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-06-14 13:47 use exact allocation for dma coherent memory Christoph Hellwig
2019-06-14 13:47 ` [PATCH 01/16] media: videobuf-dma-contig: use dma_mmap_coherent Christoph Hellwig
2019-06-14 13:47 ` [PATCH 02/16] drm/ati_pcigart: stop using drm_pci_alloc Christoph Hellwig
2019-06-14 13:47 ` [PATCH 03/16] drm/i915: " Christoph Hellwig
2019-06-14 16:45   ` [Intel-gfx] " Ville Syrjälä
2019-06-14 13:47 ` [PATCH 04/16] drm: move drm_pci_{alloc,free} to drm_legacy Christoph Hellwig
2019-06-14 13:47 ` [PATCH 05/16] drm: don't mark pages returned from drm_pci_alloc reserved Christoph Hellwig
2019-06-14 13:47 ` [PATCH 06/16] drm: don't pass __GFP_COMP to dma_alloc_coherent in drm_pci_alloc Christoph Hellwig
2019-06-14 13:47 ` [PATCH 07/16] IB/hfi1: stop passing bogus gfp flags arguments to dma_alloc_coherent Christoph Hellwig
2019-06-14 13:47 ` [PATCH 08/16] IB/qib: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 09/16] cnic: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 10/16] iwlwifi: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 11/16] s390/ism: " Christoph Hellwig
2019-06-14 13:47 ` [PATCH 12/16] staging/comedi: mark as broken Christoph Hellwig
2019-06-14 14:02   ` Greg KH
2019-06-14 14:48     ` Christoph Hellwig
2019-06-14 15:30       ` Greg KH
2019-06-14 15:34         ` Christoph Hellwig [this message]
2019-06-17 13:15           ` Ian Abbott
2019-06-14 13:47 ` [PATCH 13/16] mm: rename alloc_pages_exact_nid to alloc_pages_exact_node Christoph Hellwig
2019-06-14 13:47 ` [PATCH 14/16] mm: use alloc_pages_exact_node to implement alloc_pages_exact Christoph Hellwig
2019-06-14 13:47 ` [PATCH 15/16] dma-mapping: clear __GFP_COMP in dma_alloc_attrs Christoph Hellwig
2019-06-14 13:47 ` [PATCH 16/16] dma-mapping: use exact allocation in dma_alloc_contiguous Christoph Hellwig
2019-06-14 14:15   ` David Laight
2019-06-14 14:50     ` Christoph Hellwig
2019-06-14 15:01       ` David Laight
2019-06-14 15:05         ` Christoph Hellwig
2019-06-14 15:05       ` Robin Murphy
2019-06-14 15:08         ` Christoph Hellwig
2019-06-14 15:16         ` David Laight
2019-06-17  8:21 ` use exact allocation for dma coherent memory Dan Carpenter
2019-06-17  8:33   ` Christoph Hellwig
2019-06-19 16:29     ` Jason Gunthorpe
2019-06-20 10:51       ` Christoph Hellwig
2019-07-01  8:48 ` Christoph Hellwig
2019-07-02  9:48   ` Arend Van Spriel
2019-07-08 18:43     ` Christoph Hellwig

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