Hi Baolu, 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? Thanks, Jacob
