On Fri, Aug 04, 2023 at 10:30:12AM +0800, Baolu Lu wrote: > On 2023/8/4 10:20, Baolu Lu wrote: > > On 2023/8/3 23:18, Jason Gunthorpe wrote: > > > On Thu, Aug 03, 2023 at 12:44:03AM +0000, Tian, Kevin wrote: > > > > > From: Jason Gunthorpe<jgg@xxxxxxxx> > > > > > Sent: Wednesday, August 2, 2023 10:16 PM > > > > > > > > > > On Tue, Aug 01, 2023 at 02:31:23PM +0800, Lu Baolu wrote: > > > > > > The PCI PASID enabling interface guarantees that the > > > > > > address space used > > > > > > by each PASID is unique. This is achieved by checking that the PCI ACS > > > > > > path is enabled for the device. If the path is not enabled, then the > > > > > > PASID feature cannot be used. > > > > > > > > > > > > if (!pci_acs_path_enabled(pdev, NULL, PCI_ACS_RR | PCI_ACS_UF)) > > > > > > return -EINVAL; > > > > > > > > > > > > The PASID array is not an attribute of the IOMMU group. It is more > > > > > > natural to store the PASID array in the per-device IOMMU data. This > > > > > > makes the code clearer and easier to understand. No functional changes > > > > > > are intended. > > > > > Is there a reason to do this? > > > > > > > > > > *PCI* requires the ACS/etc because PCI kind of messed up how switches > > > > > handled PASID so PASID doesn't work otherwise. > > > > > > > > > > But there is nothing that says other bus type can't have working > > > > > (non-PCI) PASID and still have device isolation issues. > > > > > > > > > > So unless there is a really strong reason to do this we should keep > > > > > the PASID list in the group just like the domain. > > > > > > > > > this comes from the consensus in [1]. > > > > > > > > [1]https://lore.kernel.org/linux-iommu/ZAcyEzN4102gPsWC@xxxxxxxxxx/ > > > That consensus was that we don't have PASID support if there is > > > multi-device groups, at least in iommufd.. That makes sense. If we > > > want to change the core code to enforce this that also makes sense > > > > In my initial plan, I had a third patch that would have enforced single- > > device groups for PASID interfaces in the core. But I ultimately dropped > > it because it is the fact for PCI devices, but I am not sure about other > > buses although perhaps there is none. > > > > > But this series is just moving the array? > > > > So I took the first step by moving the pasid_array from iommu group to > > the device. 😄 > > In my mind, iommu_group was introduced to solve the PCI alias and P2P > transactions which bypass IOMMU translation. When we enter the PASID > world, the architecture should disallow these anymore. Hence, it's safe > to move pasid_array to device. > > This was the motivation of this series. I think you should add a protection as well, directly prevent multi-device groups being used with pasid. Jason
