From: Julien Grall <julien.grall@arm.com>
To: Christoph Hellwig <hch@lst.de>
Cc: Stefano Stabellini <sstabellini@kernel.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
x86@kernel.org, linux-kernel@vger.kernel.org,
iommu@lists.linux-foundation.org, xen-devel@lists.xenproject.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [Xen-devel] [PATCH 07/11] swiotlb-xen: provide a single page-coherent.h header
Date: Sat, 17 Aug 2019 19:20:27 +0100 [thread overview]
Message-ID: <21746bbf-618a-d12b-c767-f9e865f4dd20@arm.com> (raw)
In-Reply-To: <20190817065011.GA18599@lst.de>
Hi Christoph,
On 8/17/19 7:50 AM, Christoph Hellwig wrote:
> On Fri, Aug 16, 2019 at 11:40:43PM +0100, Julien Grall wrote:
>> I am not sure I agree with this rename. The implementation of the helpers
>> are very Arm specific as this is assuming Dom0 is 1:1 mapped.
>>
>> This was necessary due to the lack of IOMMU on Arm platforms back then.
>> But this is now a pain to get rid of it on newer platform...
>
> So if you look at the final version of the header after the whole
> series, what assumes a 1:1 mapping? It all just is
>
> if (pfn_valid())
> local cache sync;
> else
> call into the arch code;
In the context of Xen Arm, the dev_addr is a host physical address. From
my understanding pfn_valid() is dealing with a guest physical frame.
Therefore by passing PFN_DOWN(dev_addr) in argument you assume that the
host and guest address spaces are the same.
>
> are you concerned that the local cache sync might have to be split
> up more for a non-1:1 map in that case? We could just movea
> the xen_dma_* routines into the arch instead of __xen_dma, but it
> really helps to have a common interface header.
Moving xen_dma_* routines into the arch would be a good option.
Although, I would still consider a stub version for arch not requiring
specific DMA.
Cheers,
--
Julien Grall
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next prev parent reply other threads:[~2019-08-17 18:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-16 13:00 swiotlb-xen cleanups Christoph Hellwig
2019-08-16 13:00 ` [PATCH 01/11] xen/arm: use dma-noncoherent.h calls for xen-swiotlb cache maintainance Christoph Hellwig
2019-08-19 11:45 ` [Xen-devel] " Julien Grall
2019-08-26 9:20 ` Christoph Hellwig
2019-08-16 13:00 ` [PATCH 02/11] xen/arm: use dev_is_dma_coherent Christoph Hellwig
2019-08-19 11:31 ` [Xen-devel] " Julien Grall
2019-08-16 13:00 ` [PATCH 03/11] xen/arm: pass one less argument to dma_cache_maint Christoph Hellwig
2019-08-16 13:37 ` Robin Murphy
2019-08-16 16:43 ` Christoph Hellwig
2019-08-16 13:00 ` [PATCH 04/11] xen/arm: remove xen_dma_ops Christoph Hellwig
2019-08-19 11:38 ` [Xen-devel] " Julien Grall
2019-08-16 13:00 ` [PATCH 05/11] xen: remove the exports for xen_{create, destroy}_contiguous_region Christoph Hellwig
2019-08-16 13:00 ` [PATCH 06/11] swiotlb-xen: always use dma-direct helpers to alloc coherent pages Christoph Hellwig
2019-08-16 13:00 ` [PATCH 07/11] swiotlb-xen: provide a single page-coherent.h header Christoph Hellwig
2019-08-16 22:40 ` [Xen-devel] " Julien Grall
2019-08-17 6:50 ` Christoph Hellwig
2019-08-17 18:20 ` Julien Grall [this message]
2019-08-16 13:00 ` [PATCH 08/11] swiotlb-xen: use the same foreign page check everywhere Christoph Hellwig
2019-08-19 13:53 ` [Xen-devel] " Julien Grall
2019-08-16 13:00 ` [PATCH 09/11] swiotlb-xen: simplify cache maintainance Christoph Hellwig
2019-08-16 13:00 ` [PATCH 10/11] swiotlb-xen: merge xen_unmap_single into xen_swiotlb_unmap_page Christoph Hellwig
2019-08-16 13:00 ` [PATCH 11/11] arm64: use asm-generic/dma-mapping.h Christoph Hellwig
2019-08-19 7:32 ` Will Deacon
2019-08-27 2:00 ` swiotlb-xen cleanups Stefano Stabellini
2019-08-27 6:21 ` Christoph Hellwig
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