Messages in this thread | | | Date | Wed, 11 May 2022 09:00:50 +0100 | From | Jean-Philippe Brucker <> | Subject | Re: [PATCH v6 02/12] iommu: Add pasid_bits field in struct dev_iommu |
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On Wed, May 11, 2022 at 10:25:48AM +0800, Baolu Lu wrote: > On 2022/5/10 22:34, Jason Gunthorpe wrote: > > On Tue, May 10, 2022 at 02:17:28PM +0800, Lu Baolu wrote: > > > > > int iommu_device_register(struct iommu_device *iommu, > > > diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > > index 627a3ed5ee8f..afc63fce6107 100644 > > > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c > > > @@ -2681,6 +2681,8 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev) > > > smmu->features & ARM_SMMU_FEAT_STALL_FORCE) > > > master->stall_enabled = true; > > > + dev->iommu->pasid_bits = master->ssid_bits; > > > return &smmu->iommu; > > > err_free_master: > > > diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c > > > index 2990f80c5e08..99643f897f26 100644 > > > +++ b/drivers/iommu/intel/iommu.c > > > @@ -4624,8 +4624,11 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev) > > > if (pasid_supported(iommu)) { > > > int features = pci_pasid_features(pdev); > > > - if (features >= 0) > > > + if (features >= 0) { > > > info->pasid_supported = features | 1; > > > + dev->iommu->pasid_bits = > > > + fls(pci_max_pasids(pdev)) - 1; > > > + } > > > > It is not very nice that both the iommu drivers have to duplicate the > > code to read the pasid capability out of the PCI device. > > > > IMHO it would make more sense for the iommu layer to report the > > capability of its own HW block only, and for the core code to figure > > out the master's limitation using a bus-specific approach. > > Fair enough. The iommu hardware capability could be reported in > > /** > * struct iommu_device - IOMMU core representation of one IOMMU hardware > * instance > * @list: Used by the iommu-core to keep a list of registered iommus > * @ops: iommu-ops for talking to this iommu > * @dev: struct device for sysfs handling > */ > struct iommu_device { > struct list_head list; > const struct iommu_ops *ops; > struct fwnode_handle *fwnode; > struct device *dev; > }; > > I haven't checked ARM code yet, but it works for x86 as far as I can > see.
Arm also supports non-PCI PASID by reading a firmware property:
device_property_read_u32(dev, "pasid-num-bits", &master->ssid_bits);
should be the only difference
Thanks, Jean
> > > > > It is also unfortunate that the enable/disable pasid is inside the > > iommu driver as well - ideally the PCI driver itself would do this > > when it knows it wants to use PASIDs. > > > > The ordering interaction with ATS makes this look quite annoying > > though. :( > > > > I'm also not convinced individual IOMMU drivers should be forcing ATS > > on, there are performance and functional implications here. Using ATS > > or not is possibly best left as an administrator policy controlled by > > the core code. Again we seem to have some mess. > > Agreed with you. This has already been in my task list. I will start to > solve it after the iommufd tasks. > > Best regards, > baolu
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