[PATCH rc v3 2/5] iommu/arm-smmu-v3: Implement is_attach_deferred() for kdump

Nicolin Chen
2026-04-25T21:32:14Z

Though the kdump kernel adopts the crashed kernel's stream table, the iommu
core will still try to attach each probed device to a default domain, which
overwrites the adopted STE and breaks in-flight DMA from that device.

Implement an is_attach_deferred() callback to prevent this. For each device
that has STE.V=1 and STE.Cfg!=Abort in the adopted table, defer the default
domain attachment, until the device driver explicitly requests it.

Fixes: b63b3439b856 ("iommu/arm-smmu-v3: Abort all transactions if SMMU is enabled in kdump kernel")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 24 +++++++++++++++++++++
1 file changed, 24 insertions(+)

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 bf292e1e0c323..8423bcc4be69e 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -4213,6 +4213,29 @@ static void arm_smmu_remove_master(struct arm_smmu_master *master)
kfree(master->build_invs);
}

+static bool arm_smmu_is_attach_deferred(struct device *dev)
+{
+ struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+ struct arm_smmu_device *smmu = master->smmu;
+ int i;
+
+ if (!(smmu->options & ARM_SMMU_OPT_KDUMP_ADOPT))
+ return false;
+
+ for (i = 0; i < master->num_streams; i++) {
+ struct arm_smmu_ste *ste =
+ arm_smmu_get_step_for_sid(smmu, master->streams[i].id);
+ u64 ent0 = le64_to_cpu(ste->data[0]);
+
+ /* Defer only when there might be in-flight DMAs */
+ if ((ent0 & STRTAB_STE_0_V) &&
+ FIELD_GET(STRTAB_STE_0_CFG, ent0) != STRTAB_STE_0_CFG_ABORT)
+ return true;
+ }
+
+ return false;
+}
+
static struct iommu_device *arm_smmu_probe_device(struct device *dev)
{
int ret;
@@ -4375,6 +4398,7 @@ static const struct iommu_ops arm_smmu_ops = {
.hw_info = arm_smmu_hw_info,
.domain_alloc_sva = arm_smmu_sva_domain_alloc,
.domain_alloc_paging_flags = arm_smmu_domain_alloc_paging_flags,
+ .is_attach_deferred = arm_smmu_is_attach_deferred,
.probe_device = arm_smmu_probe_device,
.release_device = arm_smmu_release_device,
.device_group = arm_smmu_device_group,
--
2.43.0