Re: [PATCH v2 06/10] iommu/arm-smmu-v3: Allocate vmid in arm_vsmmu_init

Jason Gunthorpe
2026-01-26T21:16:40Z

On Wed, Jan 21, 2026 at 05:24:24PM -0800, Nicolin Chen wrote:
> VMID owned by a vSMMU should be allocated in the viommu_init callback, as
> HW like tegra241-cmdqv needs to setup VINTF with the VMID.

Even the architected SMMU needs this, the VMS (not implemented in
Linux) should all share the same VMID for the same VM.

> +void arm_vsmmu_destroy(struct iommufd_viommu *viommu)
> +{
> + struct arm_vsmmu *vsmmu = container_of(viommu, struct arm_vsmmu, core);
> +
> + mutex_lock(&arm_smmu_asid_lock);
> + ida_free(&vsmmu->smmu->vmid_map, vsmmu->vmid);
> + mutex_unlock(&arm_smmu_asid_lock);

Need a comment explaining where the flush is.

It looks like arm_smmu_iotlb_tag_free() does the free in the case of
INV_TYPE_S2_VMID_VSMMU?

But this patch doesn't have that code yet. So maybe this should be
merged with the next patch..

Jason