From: Christoph Hellwig <hch@lst.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Christoph Hellwig <hch@lst.de>,
iommu@lists.linux-foundation.org,
Vineet Gupta <vgupta@synopsys.com>,
"Matwey V. Kornilov" <matwey@sai.msu.ru>,
Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
linux-snps-arc@lists.infradead.org,
Ezequiel Garcia <ezequiel@collabora.com>,
linux-media@vger.kernel.org, linux-arm-kernel@vger.kernel.org,
dri-devel@lists.freedesktop.org, sparclinux@vger.kernel.org,
openrisc@lists.librecores.org, linux-parisc@vger.kernel.org,
linux-mips@vger.kernel.org
Subject: Re: [PATCH 02/10] arm64/iommu: don't remap contiguous allocations for coherent devices
Date: Mon, 10 Dec 2018 20:25:08 +0100 [thread overview]
Message-ID: <20181210192508.GA31318@lst.de> (raw)
In-Reply-To: <eaf8ce49-ab5e-7c02-a028-74671172b684@arm.com>
On Mon, Dec 10, 2018 at 07:19:30PM +0000, Robin Murphy wrote:
> On 08/12/2018 17:36, Christoph Hellwig wrote:
>> There is no need to have an additional kernel mapping for a contiguous
>> allocation if the device already is DMA coherent, so skip it.
>
> FWIW, the "need" was that it kept the code in this path simple and the
> mapping behaviour consistent with the regular iommu_dma_alloc() case. One
> could quite easily retort that there is no need for the extra complexity of
> this patch, since vmalloc is cheap on a 64-bit architecture ;)
Heh. Well, without the remap we do less work, we prepare for a simple
implementation of DMA_ATTR_NON_CONSISTENT, and also prepapre the code
to be better reusable for architectures that don't do remapping of
DMA allocations at all.
>> if (addr) {
>> memset(addr, 0, size);
>> - if (!coherent)
>> - __dma_flush_area(page_to_virt(page), iosize);
>> + __dma_flush_area(page_to_virt(page), iosize);
>
> Oh poo - seems I missed it at the time but the existing logic here is
> wrong. Let me send a separate fix to flip those statements into the correct
> order...
Yes, flushing the remapped alias only after zeroing it looks odd.
next prev parent reply other threads:[~2018-12-10 19:25 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-08 17:36 make the non-consistent DMA allocator more userful Christoph Hellwig
2018-12-08 17:36 ` [PATCH 01/10] dma-direct: provide a generic implementation of DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-08 17:36 ` [PATCH 02/10] arm64/iommu: don't remap contiguous allocations for coherent devices Christoph Hellwig
2018-12-10 19:19 ` Robin Murphy
2018-12-10 19:25 ` Christoph Hellwig [this message]
2018-12-08 17:36 ` [PATCH 03/10] arm64/iommu: implement support for DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-08 17:36 ` [PATCH 04/10] arm: implement DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-08 22:52 ` Ezequiel Garcia
2018-12-10 19:16 ` Christoph Hellwig
2018-12-08 17:36 ` [PATCH 05/10] sparc64/iommu: move code around a bit Christoph Hellwig
2018-12-09 4:58 ` David Miller
2018-12-08 17:36 ` [PATCH 06/10] sparc64/iommu: implement DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-09 4:58 ` David Miller
2018-12-08 17:36 ` [PATCH 07/10] sparc64/pci_sun4v: move code around a bit Christoph Hellwig
2018-12-09 4:58 ` David Miller
2018-12-08 17:37 ` [PATCH 08/10] sparc64/pci_sun4v: implement DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-09 4:58 ` David Miller
2018-12-08 17:37 ` [PATCH 09/10] dma-mapping: skip declared coherent memory for DMA_ATTR_NON_CONSISTENT Christoph Hellwig
2018-12-08 17:37 ` [PATCH 10/10] Documentation: update the description " Christoph Hellwig
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