On Wed, Sep 11, 2024 at 08:06:48AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > Sent: Wednesday, September 11, 2024 3:31 PM > > > > On Wed, Sep 11, 2024 at 07:09:15AM +0000, Tian, Kevin wrote: > > > > From: Nicolin Chen <nicolinc@xxxxxxxxxx> > > > > Sent: Wednesday, September 11, 2024 4:41 AM > > > > > > > > -3. IOMMUFD_OBJ_HW_PAGETABLE is created when an external driver > > calls > > > > the IOMMUFD > > > > +3. IOMMUFD_OBJ_HWPT_PAGING can be created in two ways: > > > > + > > > > + IOMMUFD_OBJ_HWPT_PAGING is created when an external driver > > calls > > > > the IOMMUFD > > > > kAPI to attach a bound device to an IOAS. Similarly the external driver > > uAPI > > > > allows userspace to initiate the attaching operation. If a compatible > > > > pagetable already exists then it is reused for the attachment. Otherwise > > a > > > > new pagetable object and iommu_domain is created. Successful > > > > completion of > > > > this operation sets up the linkages among IOAS, device and > > > > iommu_domain. Once > > > > - this completes the device could do DMA. > > > > - > > > > - Every iommu_domain inside the IOAS is also represented to userspace > > as > > > > a > > > > - HW_PAGETABLE object. > > > > + this completes the device could do DMA. Note that every > > iommu_domain > > > > inside > > > > + the IOAS is also represented to userspace as an > > > > IOMMUFD_OBJ_HWPT_PAGING. > > > > > > the last sentence is redundant. here we are talking about how > > HWPT_PAGING > > > is created so it's implied. probably you can state that HWPT_PAGING object > > > is created when talking about "otherwise a new page table object and > > > iommu_domain is created". > > > > I don't quite get this part...where is the redundancy? And where > > is "otherwise a new page table object .."? > > the original text: > > allows userspace to initiate the attaching operation. If a compatible > pagetable already exists then it is reused for the attachment. Otherwise a > new pagetable object and iommu_domain is created. Successful completion of > > it's clear to say that HWPT_PAGING object is created upon successful > completion there. Then naturally every iommu_domain in an IOAS > is represented to userspace as HWPT_PAGING. Not added by you > but could be cleaned up while at it. 😊 I see. I did this: +3. IOMMUFD_OBJ_HWPT_PAGING can be created in two ways: + + * IOMMUFD_OBJ_HWPT_PAGING is automatically created when an external driver + calls the IOMMUFD kAPI to attach a bound device to an IOAS. Similarly the + external driver uAPI allows userspace to initiate the attaching operation. + If a compatible member HWPT_PAGING object exists in the IOAS's HWPT_PAGING + list, then it will be reused. Otherwise a new HWPT_PAGING that represents + an iommu_domain to userspace will be created, and then added to the list. + Successful completion of this operation sets up the linkages among IOAS, + device and iommu_domain. Once this completes the device could do DMA. + + * IOMMUFD_OBJ_HWPT_PAGING can be manually created via the IOMMU_HWPT_ALLOC + uAPI, provided an ioas_id via @pt_id to associate the new HWPT_PAGING to + the corresponding IOAS object. The benefit of this manual allocation is to + allow allocation flags (defined in enum iommufd_hwpt_alloc_flags), e.g. it + allocates a nesting parent HWPT_PAGING if the IOMMU_HWPT_ALLOC_NEST_PARENT + flag is set. Thanks Nicolin
