Messages in this thread Patch in this message | | | Date | Mon, 20 Feb 2023 14:21:00 +0000 | Subject | Re: [PATCH v2 1/6] ARM/dma-mapping: Remove iommu_detach_device() | From | Robin Murphy <> |
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On 2023-02-17 09:47, Lu Baolu wrote: > iommu_detach_device() attaches the default domain to the device, or if > default domain is not supported by the IOMMU driver, it calls its > set_platform_dma_ops callback. If the default domain is supported or > the IOMMU driver is not iommu-dma aware, iommu_detach_device() is > actually a noop. > > The 64-bit ARM drivers always support default domain and iommu-dma is > even not enabled for 32-bit ARM. This turns out that iommu_detach_device() > is always a noop in arm_iommu_detach_device(). Remove it to avoid dead > code.
Huh? This call clearly balances the iommu_attach_device() call in arm_iommu_attach_device() - it has nothing to do with default domains.
> The bonus is that it also removes a obstacle of arm_iommu_detach_device() > re-entering the iommu core during release_device. With this removed, the > iommu core code could be simplified a lot.
That needs to be worked around in those release paths, not by breaking the public API. Should probably just be a case of doing as much "detach" as necessary directly, then calling arm_iommu_release_mapping(). Just beware that arm_teardown_iommu_dma_ops() may or may not have done some of it already, depending on whether a driver ever bound to the device.
Thanks, Robin.
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> > --- > arch/arm/mm/dma-mapping.c | 1 - > 1 file changed, 1 deletion(-) > > diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c > index 8bc01071474a..dcbc2f4586d4 100644 > --- a/arch/arm/mm/dma-mapping.c > +++ b/arch/arm/mm/dma-mapping.c > @@ -1699,7 +1699,6 @@ void arm_iommu_detach_device(struct device *dev) > return; > } > > - iommu_detach_device(mapping->domain, dev); > kref_put(&mapping->kref, release_iommu_mapping); > to_dma_iommu_mapping(dev) = NULL; > set_dma_ops(dev, NULL);
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