Messages in this thread | | | Date | Mon, 15 Nov 2021 09:24:42 -0400 | From | Jason Gunthorpe <> | Subject | Re: [PATCH 02/11] driver core: Set DMA ownership during driver bind/unbind |
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On Mon, Nov 15, 2021 at 05:19:02AM -0800, Christoph Hellwig wrote: > On Mon, Nov 15, 2021 at 10:05:43AM +0800, Lu Baolu wrote: > > @@ -566,6 +567,12 @@ static int really_probe(struct device *dev, struct device_driver *drv) > > goto done; > > } > > > > + if (!drv->suppress_auto_claim_dma_owner) { > > + ret = iommu_device_set_dma_owner(dev, DMA_OWNER_KERNEL, NULL); > > + if (ret) > > + return ret; > > + } > > I'd expect this to go into iommu_setup_dma_ops (and its arm and s390 > equivalents), as that is what claims an IOMMU for in-kernel usage
If iommu_device_set_dma_owner(dev_a) fails changes dynamically depending on what iommu_device_set_dma_owner(dev_b, DMA_OWNER_USER) have been done.
The whole point here is that doing a iommu_device_set_dma_owner(dev_b, DMA_OWNER_USER) needs to revoke kernel usage from a whole bunch of other devices in the same group.
revoking kernel usage means it needs to ensure that no driver is bound and prevent future drivers from being bound.
iommu_setup_dma_ops() is something done once early on in boot, not at every driver probe, so I don't see how it can help??
Jason
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