From: Christoph Hellwig <hch@infradead.org>
To: "Ørjan Eide" <Orjan.Eide@arm.com>
Cc: Brian Starkey <Brian.Starkey@arm.com>,
Liam Mark <lmark@codeaurora.org>,
"devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
"tkjos@android.com" <tkjos@android.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linaro-mm-sig@lists.linaro.org" <linaro-mm-sig@lists.linaro.org>,
"arve@android.com" <arve@android.com>,
"joel@joelfernandes.org" <joel@joelfernandes.org>,
nd <nd@arm.com>, "maco@android.com" <maco@android.com>,
"christian@brauner.io" <christian@brauner.io>
Subject: Re: [Linaro-mm-sig] [PATCH 2/4] staging: android: ion: Restrict cache maintenance to dma mapped memory
Date: Wed, 6 Feb 2019 23:31:04 -0800 [thread overview]
Message-ID: <20190207073104.GA16222@infradead.org> (raw)
In-Reply-To: <20190206154021.GC3768@e106893-lin.trondheim.arm.com>
The CPU may only access DMA mapped memory if ownership has been
transferred back to the CPU using dma_sync_{single,sg}_to_cpu, and then
before the device can access it again ownership needs to be transferred
back to the device using dma_sync_{single,sg}_to_device.
> I've run some testing, and this patch does indeed fix the crash in
> dma_sync_sg_for_cpu when it tried to use the 0 dma_address from the sg
> list.
>
> Tested-by: Ørjan Eide <orjan.eide@arm.com>
>
> I tested this on an older kernel, v4.14, since the dma-mapping code
> moved, in v4.19, to ignore the dma_address and instead use sg_phys() to
> get a valid address from the page, which is always valid in the ion sg
> lists. While this wouldn't crash on newer kernels, it's still good to
> avoid the unnecessary work when no CMO is needed.
Can you also test is with CONFIG_DMA_API_DEBUG enabled, as that should
catch all the usual mistakes in DMA API usage, including the one found?
next prev parent reply other threads:[~2019-02-07 7:31 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-18 18:37 [PATCH 0/4] ION stability and perf changes Liam Mark
2019-01-18 18:37 ` [PATCH 1/4] staging: android: ion: Support cpu access during dma_buf_detach Liam Mark
2019-01-18 19:34 ` Andrew F. Davis
2019-01-18 20:40 ` Laura Abbott
2019-01-18 18:37 ` [PATCH 2/4] staging: android: ion: Restrict cache maintenance to dma mapped memory Liam Mark
2019-01-18 20:20 ` Andrew F. Davis
2019-01-18 21:18 ` Liam Mark
2019-01-29 23:44 ` Liam Mark
2019-01-30 11:31 ` Brian Starkey
2019-02-06 15:40 ` [Linaro-mm-sig] " Ørjan Eide
2019-02-07 7:31 ` Christoph Hellwig [this message]
2019-02-07 15:45 ` Ørjan Eide
2019-02-28 23:49 ` Liam Mark
2019-01-30 14:31 ` Andrew F. Davis
2019-01-18 18:37 ` [PATCH 3/4] dma-buf: add support for mapping with dma mapping attributes Liam Mark
2019-01-18 20:48 ` Laura Abbott
2019-01-18 21:32 ` Liam Mark
2019-01-18 22:45 ` Laura Abbott
2019-01-19 10:25 ` Christoph Hellwig
2019-01-19 16:50 ` Laura Abbott
2019-01-21 8:30 ` Christoph Hellwig
2019-01-21 19:44 ` Liam Mark
2019-01-21 19:49 ` Andrew F. Davis
2019-01-21 20:20 ` Liam Mark
2019-01-21 20:24 ` Andrew F. Davis
2019-01-21 22:18 ` Liam Mark
2019-01-22 15:42 ` Andrew F. Davis
2019-01-22 22:47 ` Liam Mark
2019-01-21 21:30 ` Christoph Hellwig
2019-01-21 22:14 ` Liam Mark
2019-01-21 21:29 ` Christoph Hellwig
2019-01-21 22:12 ` Liam Mark
2019-01-22 16:06 ` Andrew F. Davis
2019-01-22 22:50 ` Liam Mark
2019-01-18 18:37 ` [PATCH 4/4] staging: android: ion: Support " Liam Mark
2019-01-21 12:19 ` Brian Starkey
2019-01-22 22:37 ` Liam Mark
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