Messages in this thread | | | Date | Mon, 25 Jul 2022 11:47:58 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v10 08/12] iommu/sva: Refactoring iommu_sva_bind/unbind_device() |
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On Mon, Jul 25, 2022 at 06:22:06PM +0800, Baolu Lu wrote: > On 2022/7/25 15:50, Tian, Kevin wrote: > > > From: Baolu Lu <baolu.lu@linux.intel.com> > > > Sent: Sunday, July 24, 2022 9:48 PM > > > > > > > > The API is really refcounting the PASID: > > > > > > > > > +struct iommu_sva *iommu_sva_bind_device(struct device *dev, > > > > > + struct mm_struct *mm); > > > > > +void iommu_sva_unbind_device(struct iommu_sva *handle); > > > > > > > > So what you need to do is store that 'iommu_sva' in the group's PASID > > > > xarray. > > > > > > > > The bind logic would be > > > > > > > > sva = xa_load(group->pasid, mm->pasid) > > > > if (sva) > > > > refcount_inc(sva->users) > > > > return sva > > > > sva = kalloc > > > > sva->domain = domain > > > > xa_store(group->pasid, sva); > > > > > > Thanks for the suggestion. It makes a lot of sense to me. > > > > > > Furthermore, I'd like to separate the generic data from the caller- > > > specific things because the group->pasid_array should also be able to > > > serve other usages. Hence, the attach/detach_device_pasid interfaces > > > might be changed like below: > > > > > > /* Collection of per-pasid IOMMU data */ > > > struct group_pasid { > > > struct iommu_domain *domain; > > > void *priv; > > > }; > > > > > > > Is there any reason why pasid refcnt is sva specific and needs to be > > in a priv field? > > I am going to store the iommu_sva data which represents the bind > relationship between device and domain.
Why do you need that?
If you are starting at the pasid xarray then you already know the group/device, so we don't need to store it again.
The only thing needed is the refcount so just store a refcount in this structure and be done with it. If someone needs to add something later then we can use a union or something, but right now adding an untagged void * is bad.
Jason
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