Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 11 Jul 2023 11:18:54 -0300 | From | Jason Gunthorpe <> | Subject | Re: [RFC PATCH 5/6] iommu: Support mm PASID 1:1 with sva domain |
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On Tue, Jul 11, 2023 at 10:43:43AM +0800, Baolu Lu wrote: > On 2023/7/11 1:28, Jason Gunthorpe wrote: > > > @@ -88,31 +98,41 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm > > > goto out_unlock; > > > } > > > - if (domain) { > > > - domain->users++; > > > - goto out; > > > + if (unlikely(domain)) { > > > + /* Re-attach the device to the same domain? */ > > > + if (domain == sva_domain) { > > > + goto out; > > > + } else { > > > + /* Didn't get detached from the previous domain? */ > > > + ret = -EBUSY; > > > + goto out_unlock; > > > + } > > > } > > And if we do all of this we should just get rid of the horrible > > iommu_get_domain_for_dev_pasid() entirely. > > At the core level, we have no idea about whether an sva domain allocated > for one device is compatible with another device. Hence, we should loop > the sva domains in the list and if the attach interface feeds back > -EINVAL's (not compatible), we should allocate a new domain for the > attached device and put it in the list if the new attachment is > successful.
Yes, generally.
It would be good to undertand if the drivers desire one sva domain per instance or one sva domain per driver - but with this approach it becomes a driver choice which to use. I would guess that one sva domain per instance is slightly simpler in the drivers..
iommu_get_domain_for_dev_pasid() turns into a check if the group already has a SVA domain bound from a list, ie we turn it upside down and have it search the list under the xa_lock instead of trying to return a domain pointer back out.
Jason
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