Re: [PATCH 14/17] iommu: remove DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE

On 2021-03-11 08:26, Christoph Hellwig wrote:

On Wed, Mar 10, 2021 at 06:39:57PM +0000, Robin Murphy wrote:

quoted

quoted

Actually... Just mirroring the iommu_dma_strict value into
struct iommu_domain should solve all of that with very little
boilerplate code.

Yes, my initial thought was to directly replace the attribute with a
common flag at iommu_domain level, but since in all cases the behaviour
is effectively global rather than actually per-domain, it seemed
reasonable to take it a step further. This passes compile-testing for
arm64 and x86, what do you think?

It seems to miss a few bits, and also generally seems to be not actually
apply to recent mainline or something like it due to different empty
lines in a few places.

Yeah, that was sketched out on top of some other development patches, 
and in being so focused on not breaking any of the x86 behaviours I did 
indeed overlook fully converting the SMMU drivers... oops!

(my thought was to do the conversion for its own sake, then clean up the 
redundant attribute separately, but I guess it's fine either way)

Let me know what you think of the version here:

http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/iommu-cleanup

I'll happily switch the patch to you as the author if you're fine with
that as well.

I still have reservations about removing the attribute API entirely and 
pretending that io_pgtable_cfg is anything other than a SoC-specific 
private interface, but the reworked patch on its own looks reasonable to 
me, thanks! (I wasn't too convinced about the iommu_cmd_line wrappers 
either...) Just iommu_get_dma_strict() needs an export since the SMMU 
drivers can be modular - I consciously didn't add that myself since I 
was mistakenly thinking only iommu-dma would call it.

Robin.
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