From 81c45c62dc3eefd83af8eb8df10e45705e8e3a47 Mon Sep 17 00:00:00 2001 From: Nicolin Chen Date: Mon, 3 Nov 2025 09:27:55 -0800 Subject: iommu/arm-smmu-v3-iommufd: Allow attaching nested domain for GBPA cases A vDEVICE has been a hard requirement for attaching a nested domain to the device. This makes sense when installing a guest STE, since a vSID must be present and given to the kernel during the vDEVICE allocation. But, when CR0.SMMUEN is disabled, VM doesn't really need a vSID to program the vSMMU behavior as GBPA will take effect, in which case the vSTE in the nested domain could have carried the bypass or abort configuration in GBPA register. Thus, having such a hard requirement doesn't work well for GBPA. Skip vmaster allocation in arm_smmu_attach_prepare_vmaster() for an abort or bypass vSTE. Note that device on this attachment won't report vevents. Update the uAPI doc accordingly. Link: https://patch.msgid.link/r/20251103172755.2026145-1-nicolinc@nvidia.com Tested-by: Shameer Kolothum Signed-off-by: Nicolin Chen Reviewed-by: Jason Gunthorpe Reviewed-by: Pranjal Shrivastava Tested-by: Shuai Xue Signed-off-by: Jason Gunthorpe --- drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-) (limited to 'drivers') diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c index 8cd8929bbfdf..e5fbbdbdea24 100644 --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c @@ -99,6 +99,8 @@ static void arm_smmu_make_nested_domain_ste( int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state, struct arm_smmu_nested_domain *nested_domain) { + unsigned int cfg = + FIELD_GET(STRTAB_STE_0_CFG, le64_to_cpu(nested_domain->ste[0])); struct arm_smmu_vmaster *vmaster; unsigned long vsid; int ret; @@ -107,8 +109,17 @@ int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state, ret = iommufd_viommu_get_vdev_id(&nested_domain->vsmmu->core, state->master->dev, &vsid); - if (ret) + /* + * Attaching to a translate nested domain must allocate a vDEVICE prior, + * as CD/ATS invalidations and vevents require a vSID to work properly. + * A abort/bypass domain is allowed to attach w/o vmaster for GBPA case. + */ + if (ret) { + if (cfg == STRTAB_STE_0_CFG_ABORT || + cfg == STRTAB_STE_0_CFG_BYPASS) + return 0; return ret; + } vmaster = kzalloc(sizeof(*vmaster), GFP_KERNEL); if (!vmaster) -- cgit