Messages in this thread | | | Date | Tue, 26 Jul 2022 16:47:00 +0800 | Subject | Re: [PATCH v10 08/12] iommu/sva: Refactoring iommu_sva_bind/unbind_device() | From | Baolu Lu <> |
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On 2022/7/25 22:47, Jason Gunthorpe wrote: > 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.
Fair enough. I will update it accordingly.
Best regards, baolu
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