Hi Baolu, On Wed, 19 Apr 2023 10:40:46 +0800, Baolu Lu <baolu.lu@xxxxxxxxxxxxxxx> wrote: > On 4/19/23 7:04 AM, Jacob Pan wrote: > > On Tue, 18 Apr 2023 10:06:12 +0800, Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx> > > wrote: > > > >> On 4/18/23 12:46 AM, Jacob Pan wrote: > >>> On Wed, 12 Apr 2023 09:37:48 +0800, Baolu Lu<baolu.lu@xxxxxxxxxxxxxxx> > >>> wrote: > >>> > >>>> On 4/11/23 4:02 PM, Tian, Kevin wrote: > >>>>>> From: Jacob Pan<jacob.jun.pan@xxxxxxxxxxxxxxx> > >>>>>> Sent: Saturday, April 8, 2023 2:06 AM > >>>>>> @@ -28,8 +26,8 @@ static int iommu_sva_alloc_pasid(struct mm_struct > >>>>>> *mm, ioasid_t min, ioasid_t ma > >>>>>> goto out; > >>>>>> } > >>>>>> > >>>>>> - ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, > >>>>>> GFP_KERNEL); > >>>>>> - if (ret < min) > >>>>>> + ret = iommu_alloc_global_pasid(min, max); > >>>>> I wonder whether this can take a device pointer so > >>>>> dev->iommu->max_pasids is enforced inside the alloc function. > >>>> Agreed. Instead of using the open code, it looks better to have a > >>>> helper like dev_iommu_max_pasids(). > >>> yes, probably export dev_iommu_get_max_pasids(dev)? > >>> > >>> But if I understood Kevin correctly, he's also suggesting that the > >>> interface should be changed to iommu_alloc_global_pasid(dev), my > >>> concern is that how do we use this function to reserve RID_PASID which > >>> is not specific to a device? > >> Probably we can introduce a counterpart dev->iommu->min_pasids, so that > >> there's no need to reserve the RID_PASID. At present, we can set it to > >> 1 in the core as ARM/AMD/Intel all treat PASID 0 as a special pasid. > >> > >> In the future, if VT-d supports using arbitrary number as RID_PASID for > >> any specific device, we can call iommu_alloc_global_pasid() for that > >> device. > >> > >> The device drivers don't know and don't need to know the range of > >> viable PASIDs, so the @min, @max parameters seem to be unreasonable. > > Sure, that is reasonable. Another question is whether global PASID > > allocation is always for a single device, if not I prefer to keep the > > current iommu_alloc_global_pasid() and add a wrapper > > iommu_alloc_global_pasid_dev(dev) to extract the @min, @max. OK? > > No problem from the code perspective. But we only need one API. > > We can now add the kAPI that we really need. In this series, the idxd > driver wants to allocate a global PASID for its kernel dma with pasid > purpose. So, iommu_alloc_global_pasid_dev() seems to be sufficient. > > If, in the future, we will have a need to provide global pasid > allocation other than device drivers, we can easily add the variants. > sounds good, I will only add iommu_alloc_global_pasid_dev(dev). let the core code set @min, @max for devices. Thanks, Jacob
