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Currently its enforced >> using PASID check. It worked fine as most GPU's has PASID feature. But >> this means, identity mode enforcement is done for all PASID capable devices. >> >> Previously it made sense as domain allocation API >> (iommu_ops->domain_alloc()) was just passing domain type. So it couldn't >> check device capability and decide best suited page table type (v1 or >> v2). With recent enhancement to driver code, it uses >> domain_alloc_paging_flags() ops for all paging mode domain allocation. >> This can check device/flags and allocate best suited page table (v1 or v2). >> Hence fix amd_iommu_def_domain_type() to force identity mapping for selected >> GPUs only. >> >> With this change system booted with DMA translation mode will select: >> * Guest (v2) page table for PASID capable device >> * Host (v1) page table for non-PASID capable device >> >> Cc: Alex Deucher >> Cc: Mario Limonciello >> Signed-off-by: Vasant Hegde >> Tested-by: Amandeep Kaur Longia >> --- >> drivers/iommu/amd/iommu.c | 56 +++++++++++++++++++++++++++++++-------- >> 1 file changed, 45 insertions(+), 11 deletions(-) >> >> diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c >> index 563f9c2672d5..fe642e33c87d 100644 >> --- a/drivers/iommu/amd/iommu.c >> +++ b/drivers/iommu/amd/iommu.c >> @@ -3112,6 +3112,32 @@ static bool amd_iommu_is_attach_deferred(struct device *dev) >> return dev_data->defer_attach; >> } >> >> +static bool quirks_force_identity_mapping(struct pci_dev *pdev) >> +{ >> + struct pci_dev *root_port; >> + int class = pdev->class >> 8; >> + >> + /* AMD GPU vendor ID */ >> + if (pdev->vendor != PCI_VENDOR_ID_ATI) >> + return false; >> + >> + /* GPU class */ >> + if (class != PCI_CLASS_DISPLAY_VGA && >> + class != PCI_CLASS_DISPLAY_OTHER) >> + return false; >> + >> + root_port = pcie_find_root_port(pdev); >> + if (!root_port) >> + return false; >> + >> + /* If bridge vendor is not ATI then its APU and force IDENTITY mode */ >> + if (root_port->vendor != PCI_VENDOR_ID_ATI) >> + return true; > > Hi Vasant, > > For a discrete GPU, pcie_find_root_port() may walk up to the system root port. > On an AMD platform that root port is vendored PCI_VENDOR_ID_AMD, which is not ATI. We want to filter based on vendor as ATI only. As Mario pointed out, logic got inverted. Will fix it in v2. -Vasant