Messages in this thread | | | Date | Fri, 4 Aug 2023 10:20:28 +0800 | Subject | Re: [PATCH 0/2] iommu: Make pasid array per device | From | Baolu Lu <> |
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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@ziepe.ca> >>> 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@nvidia.com/ > 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. :-)
Best regards, baolu
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