On Mon, Jan 30, 2023 at 02:47:32PM -0400, Jason Gunthorpe wrote: > On Mon, Jan 30, 2023 at 12:38:10PM -0600, Bjorn Helgaas wrote: > > > Sorry, I'm still confused. PCI_PASID_XLATED_REQ_ONLY is a > > device-specific property, and you want to opt-in AMD graphics devices. > > Where's the AMD graphics-specific change? The current patch does > > this: > > > > pdev_pri_ats_enable > > pci_enable_pasid(pdev, 0, PCI_PASID_XLATED_REQ_ONLY) > > > > which looks like it does it for *all* devices below an AMD IOMMU, > > without any device or driver input. > > AMD GPU has a private interface to AMD IOMMU to support PASID support > that only it uses. What is it that makes this a private interface? It seems like we will end up enabling PASID on any device below an AMD v2 IOMMU. I do see the DRM amdgpu_amdkfd_device_init() path that ends up at domain_enable_v2(). Maybe that's it? But amd_iommu_domain_alloc() also leads to domain_enable_v2(), and that's pretty generic, so it looks like we set PD_IOMMUV2_MASK whenever the IOMMU supports it. And it seems like we call pci_enable_pasid() for all endpoints below a v2 IOMMU. Of course, if the endpoint doesn't have a PASID cap, pci_enable_pasid() fails (and pdev_pri_ats_enable() probably splats useless warnings when we try to disable PRI and PASID which haven't been enabled). I guess I'm trying to convince myself that no harm in enabling PASID for any device below an AMD v2 IOMMU. But I don't think a device is *required* to use translated addresses with PASID, and if it uses untranslated addresses with PASID, don't we need ACS to avoid misrouting? Bjorn
