From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Sumit Garg <sumit.garg@linaro.org>,
Christoph Hellwig <hch@lst.de>,
Greg KH <gregkh@linuxfoundation.org>,
obayashi.yoshimasa@socionext.com, m.szyprowski@samsung.com,
iommu@lists.linux-foundation.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
stable <stable@vger.kernel.org>,
Daniel Thompson <daniel.thompson@linaro.org>
Subject: Re: DMA direct mapping fix for 5.4 and earlier stable branches
Date: Tue, 9 Feb 2021 16:50:58 +0100 [thread overview]
Message-ID: <20210209155058.GA8912@lst.de> (raw)
In-Reply-To: <e36b8a7d-a999-da09-d7d9-cc26579a65d1@arm.com>
On Tue, Feb 09, 2021 at 12:45:11PM +0000, Robin Murphy wrote:
> It's not a bug, it's a fundamental design failure. dma_get_sgtable() has
> only ever sort-of-worked for DMA buffers that come from CMA or regular page
> allocations. In particular, a "no-map" DMA pool is not backed by kernel
> memory, so does not have any corresponding page structs, so it's impossible
> to generate a *valid* scatterlist to represent memory from that pool,
> regardless of what you might get away with provided you don't poke too hard
> at it.
>
> It is not a good API...
Yes, I don't think anyone should add new users of the API.
That being said the commit he is trying to backport fixes a bug in
the implementation that at least in theory could also affect in-tree
drivers.
next prev parent reply other threads:[~2021-02-09 15:52 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-09 6:09 DMA direct mapping fix for 5.4 and earlier stable branches Sumit Garg
2021-02-09 6:58 ` Greg Kroah-Hartman
2021-02-09 7:58 ` Sumit Garg
2021-02-09 8:04 ` Greg Kroah-Hartman
2021-02-09 9:05 ` obayashi.yoshimasa
2021-02-09 9:23 ` Greg KH
2021-02-09 9:36 ` Christoph Hellwig
2021-02-09 12:36 ` Sumit Garg
2021-02-09 12:45 ` Robin Murphy
2021-02-09 15:50 ` Christoph Hellwig [this message]
2021-02-09 10:19 ` obayashi.yoshimasa
2021-02-09 10:39 ` Greg KH
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