[RFC PATCH v1 4/9] iommu/arm-smmu-v3: Implement Live Update Stream Table restoration
Pranjal Shrivastava
praan at google.com
Tue Sep 29 00:19:45 PDT 2026
During the boot phase of a Kexec Handover (KHO), the incoming kernel
must adopt the preserved SMMU Stream Table to seamlessly inherit the
IOMMU state from the outgoing kernel.
Restore it in arm_smmu_init_strtab() using the kexec helpers to validate
the live STRTAB_BASE{,_CFG} and reserve the in-use ASIDs/VMIDs. Enable
ARM_SMMU_V3_KEXEC for IOMMU_LIVEUPDATE for this.
Signed-off-by: Pranjal Shrivastava <praan at google.com>
---
drivers/iommu/arm/Kconfig | 2 +-
.../arm/arm-smmu-v3/arm-smmu-v3-liveupdate.c | 142 ++++++++++++++++++
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 4 +
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 6 +
4 files changed, 153 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/arm/Kconfig b/drivers/iommu/arm/Kconfig
index ad1693e3b9c8..8f98d3ad984a 100644
--- a/drivers/iommu/arm/Kconfig
+++ b/drivers/iommu/arm/Kconfig
@@ -113,7 +113,7 @@ config ARM_SMMU_V3_IOMMUFD
# Common helpers for a kexec'd kernel, e.g. kdump adoption and live update
config ARM_SMMU_V3_KEXEC
- def_bool CRASH_DUMP
+ def_bool CRASH_DUMP || IOMMU_LIVEUPDATE
config ARM_SMMU_V3_KUNIT_TEST
tristate "KUnit tests for arm-smmu-v3 driver" if !KUNIT_ALL_TESTS
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-liveupdate.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-liveupdate.c
index 38b9d4e4ab4d..4998234e1e7a 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-liveupdate.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-liveupdate.c
@@ -429,4 +429,146 @@ void arm_smmu_unpreserve(struct iommu_device *iommu,
arm_smmu_unpreserve_strtab_linear(smmu, iommu_ser);
}
+static int arm_smmu_liveupdate_restore_strtab_2lvl(struct arm_smmu_device *smmu,
+ struct iommu_hw_ser *iommu_ser,
+ u32 cfg_reg, phys_addr_t base)
+{
+ struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
+ u32 num_l1_ents, i;
+ u64 *l2_states;
+ int ret;
+
+ if (!iommu_ser->smmuv3.l2_strtab_lu_states_phys)
+ return -EINVAL;
+ l2_states = phys_to_virt(iommu_ser->smmuv3.l2_strtab_lu_states_phys);
+
+ ret = arm_smmu_kexec_parse_strtab_2lvl(smmu, cfg_reg, base,
+ &num_l1_ents);
+ if (ret)
+ goto out_free_states;
+ cfg->l2.num_l1_ents = num_l1_ents;
+
+ ret = -ENOMEM;
+ cfg->l2.l1tab = dmam_restore_coherent_allocation(smmu->dev,
+ num_l1_ents * sizeof(*cfg->l2.l1tab), &cfg->l2.l1_dma,
+ GFP_KERNEL, iommu_ser->smmuv3.l1_strtab_lu_state);
+ if (!cfg->l2.l1tab)
+ goto out_free_states;
+
+ cfg->l2.l2ptrs = devm_kcalloc(smmu->dev, num_l1_ents,
+ sizeof(*cfg->l2.l2ptrs), GFP_KERNEL);
+ if (!cfg->l2.l2ptrs)
+ goto out_free_states;
+
+ /* The outgoing .shutdown cleared the L1 STDs of unpreserved L2 tables */
+ for (i = 0; i < num_l1_ents; i++) {
+ u64 l1_desc = le64_to_cpu(cfg->l2.l1tab[i].l2ptr);
+ phys_addr_t l2_base;
+ dma_addr_t l2_dma;
+
+ ret = arm_smmu_kexec_check_strtab_l1_desc(smmu, l1_desc, i,
+ &l2_base);
+ if (ret == 1)
+ continue;
+ if (ret)
+ goto out_free_states;
+
+ if (!l2_states[i]) {
+ dev_err(smmu->dev, "L1[%u] has no preserved L2 table\n",
+ i);
+ ret = -EINVAL;
+ goto out_free_states;
+ }
+
+ l2_dma = l2_base;
+ cfg->l2.l2ptrs[i] = dmam_restore_coherent_allocation(smmu->dev,
+ sizeof(*cfg->l2.l2ptrs[i]), &l2_dma, GFP_KERNEL,
+ l2_states[i]);
+ if (!cfg->l2.l2ptrs[i]) {
+ ret = -ENOMEM;
+ goto out_free_states;
+ }
+ }
+ ret = 0;
+
+out_free_states:
+ kho_restore_free(l2_states);
+ return ret;
+}
+
+static int
+arm_smmu_liveupdate_restore_strtab_linear(struct arm_smmu_device *smmu,
+ struct iommu_hw_ser *iommu_ser,
+ u32 cfg_reg, phys_addr_t base)
+{
+ struct arm_smmu_strtab_cfg *cfg = &smmu->strtab_cfg;
+ u32 num_ents;
+ int ret;
+
+ ret = arm_smmu_kexec_parse_strtab_linear(smmu, cfg_reg, base,
+ &num_ents);
+ if (ret)
+ return ret;
+ cfg->linear.num_ents = num_ents;
+
+ cfg->linear.table = dmam_restore_coherent_allocation(smmu->dev,
+ num_ents * sizeof(*cfg->linear.table),
+ &cfg->linear.ste_dma, GFP_KERNEL,
+ iommu_ser->smmuv3.l1_strtab_lu_state);
+ if (!cfg->linear.table)
+ return -ENOMEM;
+ return 0;
+}
+
+/*
+ * Take over the stream table left programmed by the previous kernel and
+ * reserve the ASIDs/VMIDs used by the preserved STEs. Returns -ENOENT if
+ * nothing was preserved for this SMMU.
+ */
+int arm_smmu_liveupdate_restore_strtab(struct arm_smmu_device *smmu)
+{
+ u32 cfg_reg = readl_relaxed(smmu->base + ARM_SMMU_STRTAB_BASE_CFG);
+ u64 base_reg = readq_relaxed(smmu->base + ARM_SMMU_STRTAB_BASE);
+ bool is_2lvl = smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB;
+ phys_addr_t base = base_reg & STRTAB_BASE_ADDR_MASK;
+ u32 fmt = FIELD_GET(STRTAB_BASE_CFG_FMT, cfg_reg);
+ struct iommu_hw_ser *iommu_ser;
+ int ret;
+
+ iommu_ser = iommu_get_preserved_data(smmu->base_phys, IOMMU_ARM_SMMUV3);
+ if (!iommu_ser)
+ return -ENOENT;
+
+ if (cfg_reg != iommu_ser->smmuv3.strtab_base_cfg) {
+ dev_err(smmu->dev, "STRTAB_BASE_CFG changed across live update\n");
+ return -EINVAL;
+ }
+
+ /* The preserving kernel always uses a 2-level table when supported */
+ if (fmt == STRTAB_BASE_CFG_FMT_2LVL && is_2lvl)
+ ret = arm_smmu_liveupdate_restore_strtab_2lvl(smmu, iommu_ser,
+ cfg_reg, base);
+ else if (fmt == STRTAB_BASE_CFG_FMT_LINEAR && !is_2lvl)
+ ret = arm_smmu_liveupdate_restore_strtab_linear(smmu, iommu_ser,
+ cfg_reg, base);
+ else
+ ret = -EINVAL;
+ if (ret) {
+ dev_err(smmu->dev, "failed to restore stream table: %d\n", ret);
+ return ret;
+ }
+
+ /* Keep new domains off the ASIDs/VMIDs used by the preserved STEs */
+ ret = arm_smmu_kexec_scan_and_resv_ids(smmu);
+ if (ret) {
+ dev_err(smmu->dev, "failed to reserve in-use ASIDs/VMIDs\n");
+ arm_smmu_kexec_unresv_ids(smmu);
+ return ret;
+ }
+
+ dev_info(smmu->dev, "restored preserved %s stream table\n",
+ is_2lvl ? "2-level" : "linear");
+ return 0;
+}
+
#endif
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index ae4a1c98228c..c8bcf901f1c8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4772,6 +4772,10 @@ static int arm_smmu_init_strtab(struct arm_smmu_device *smmu)
!arm_smmu_kdump_adopt_strtab(smmu))
return 0;
+ ret = arm_smmu_liveupdate_restore_strtab(smmu);
+ if (ret != -ENOENT)
+ return ret;
+
if (smmu->features & ARM_SMMU_FEAT_2_LVL_STRTAB)
ret = arm_smmu_init_strtab_2lvl(smmu);
else
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 7bce5bbe75e5..6b75f48671f8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -1208,6 +1208,12 @@ void arm_smmu_unpreserve_device(struct device *dev,
struct iommu_device_ser *device_ser);
void arm_smmu_unpreserve(struct iommu_device *iommu,
struct iommu_hw_ser *iommu_ser);
+int arm_smmu_liveupdate_restore_strtab(struct arm_smmu_device *smmu);
+#else
+static inline int arm_smmu_liveupdate_restore_strtab(struct arm_smmu_device *smmu)
+{
+ return -ENOENT;
+}
#endif
static inline void arm_smmu_domain_free(struct arm_smmu_domain *smmu_domain)
--
2.56.0.rc1.315.gc6ed9934b7-goog
More information about the kexec
mailing list