Hi, On 20/10/2023 20:48, Julien Grall wrote: > > > Hi, > > On 04/10/2023 15:55, Stewart Hildebrand wrote: >> A device tree node for a PCIe root controller may have an iommu-map property >> [1] >> with a phandle reference to the SMMU node, but not necessarily an iommus >> property. In this case, we want to treat it the same as we currently handle >> devices with an iommus property: don't pass the iommu related properties to >> hwdom. >> >> [1] >> https://www.kernel.org/doc/Documentation/devicetree/bindings/pci/pci-iommu.txt >> >> Reported-by: Michal Orzel <[email protected]> >> Signed-off-by: Stewart Hildebrand <[email protected]> > > Acked-by: Julien Grall <[email protected]> > >> --- >> v4->v5: >> * new patch >> --- >> xen/arch/arm/domain_build.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c >> index 24c9019cc43c..7da254709d17 100644 >> --- a/xen/arch/arm/domain_build.c >> +++ b/xen/arch/arm/domain_build.c >> @@ -1135,6 +1135,8 @@ static int __init write_properties(struct domain *d, >> struct kernel_info *kinfo, >> * should be skipped. >> */ >> iommu_node = dt_parse_phandle(node, "iommus", 0); >> + if ( !iommu_node ) >> + iommu_node = dt_parse_phandle(node, "iommu-map", 1); >> if ( iommu_node && device_get_class(iommu_node) != DEVICE_IOMMU ) >> iommu_node = NULL; > > I was looking at the history to understand why we decided to not always > hide the properties. > > AFAICT, this was mainly to avoid removing the master properties but > keeping the IOMMU nodes in the DT. However, in reality, I don't expect > the IOMMU to function properly in dom0 (in particular when grants are > used for DMA). > > Looking at the bindings, it turns out that all the IOMMU using the > generic bindigns would contain the property #iommu-cells. So we could > remove any device with such property. > > This would not work for IOMMU bindings not using the generic one. AFAIK, > this is only legacy SMMUv{1,2} binding so we could filter them by > compatible. > > With that we would unconditionally remove the properties iommu-* and > avoid increasing the complexity. > > Any thoughts? I think it is a good idea to skip all IOMMU nodes and properties and not only the ones recognized by Xen. I realized that it may have an impact on Rahul's RFC vSMMU series but I checked the patches and impact is negligible. As for supporting legacy bindings, I think we would be good if we search for #iommu-cells || mmu-masters.
~Michal
