On Thu, Jan 15, 2026 at 09:13:00PM -0800, Nicolin Chen wrote:

On Fri, Jan 02, 2026 at 11:57:15AM -0400, Jason Gunthorpe wrote:

quoted

On Tue, Dec 30, 2025 at 10:52:53AM -0800, Nicolin Chen wrote:

quoted

Hi Jason,

On Fri, Dec 19, 2025 at 01:05:51PM -0400, Jason Gunthorpe wrote:

quoted

+static int arm_smmu_get_tag(struct arm_smmu_domain *smmu_domain,
+			    struct arm_smmu_master *master,
+			    struct arm_vsmmu *vsmmu,
+			    struct arm_smmu_iotlb_tag *tag, bool no_alloc)

[...]

quoted

+	case ARM_SMMU_DOMAIN_S2:
+		if (smmu_domain->nest_parent) {
+			/* FIXME we can support attaching a nest_parent without
+			 * a vsmmu, but to do that we need to fix
+			 * arm_smmu_get_id_from_invs() to never return the vmid
+			 * of a vsmmu. Probably by making a
+			 * INV_TYPE_S2_VMID_VSMMU */
+			id = vsmmu->vmid;
+			return 0;
+		}

Would you mind elaborating why arm_smmu_get_id_from_invs() can't
return vsmmu->vmid to share with a naked S2 STE?

A "naked" S2 domain doesn't have a pointer to the vsmmu, so it is
impossible to get vsmmu->vmid.

An S2 parent domain should be per VM. And a vSMMU on top of an S2
should be per SMMU. So, it could have stored a list of vSMMUs and
device attaching to a naked S2 could match its master->smmu with
vSMMU->smmu in the list?

That would cause lifecycle problems if the vSMMU is destroyed
while the nake S2 is still attached and trying to use the vSMMU's
VMID.

Jason