[PATCH rc v3 4/5] iommu/arm-smmu-v3: Skip EVTQ/PRIQ setup in kdump kernel

Nicolin Chen
2026-04-25T21:32:16Z

In kdump cases, the crashed kernel's CDs and page tables can be corrupted,
which could trigger event spamming. Also, we cannot serve page requests.

Skip the EVTQ/PRIQ setup entirely rather than enabling then disabling them.

Skip the IRQ setup and guard their thread functions as well.

Also add some inline comments explaining that.

Fixes: b63b3439b856 ("iommu/arm-smmu-v3: Abort all transactions if SMMU is enabled in kdump kernel")
Cc: stable@vger.kernel.org # v6.12+
Suggested-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 66 +++++++++++++++------
1 file changed, 48 insertions(+), 18 deletions(-)

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 b6aade469a6b6..f0ab0b640a3bb 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2269,6 +2269,14 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);

+ /*
+ * A combined IRQ might call into this function with the queue disabled.
+ * E.g. kdump, where stale HW PROD vs SW CONS would drive a bogus drain
+ * and a CONS write to a disabled queue.
+ */
+ if (!(readl_relaxed(smmu->base + ARM_SMMU_CR0) & CR0_EVTQEN))
+ return IRQ_HANDLED;
+
do {
while (!queue_remove_raw(q, evt)) {
arm_smmu_decode_event(smmu, evt, &event);
@@ -2337,6 +2345,14 @@ static irqreturn_t arm_smmu_priq_thread(int irq, void *dev)
struct arm_smmu_ll_queue *llq = &q->llq;
u64 evt[PRIQ_ENT_DWORDS];

+ /*
+ * A combined IRQ might call into this function with the queue disabled.
+ * E.g. kdump, where stale HW PROD vs SW CONS would drive a bogus drain
+ * and a CONS write to a disabled queue.
+ */
+ if (!(readl_relaxed(smmu->base + ARM_SMMU_CR0) & CR0_PRIQEN))
+ return IRQ_HANDLED;
+
do {
while (!queue_remove_raw(q, evt))
arm_smmu_handle_ppr(smmu, evt);
@@ -4941,7 +4957,10 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
{
int ret, irq;
- u32 irqen_flags = IRQ_CTRL_EVTQ_IRQEN | IRQ_CTRL_GERROR_IRQEN;
+ u32 irqen_flags = IRQ_CTRL_GERROR_IRQEN;
+
+ if (!is_kdump_kernel())
+ irqen_flags |= IRQ_CTRL_EVTQ_IRQEN;

/* Disable IRQs first */
ret = arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
@@ -4967,7 +4986,7 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
} else
arm_smmu_setup_unique_irqs(smmu);

- if (smmu->features & ARM_SMMU_FEAT_PRI)
+ if (!is_kdump_kernel() && (smmu->features & ARM_SMMU_FEAT_PRI))
irqen_flags |= IRQ_CTRL_PRIQ_IRQEN;

/* Enable interrupt generation on the SMMU */
@@ -5118,21 +5137,35 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
cmd.opcode = CMDQ_OP_TLBI_NSNH_ALL;
arm_smmu_cmdq_issue_cmd_with_sync(smmu, &cmd);

- /* Event queue */
- writeq_relaxed(smmu->evtq.q.q_base, smmu->base + ARM_SMMU_EVTQ_BASE);
- writel_relaxed(smmu->evtq.q.llq.prod, smmu->page1 + ARM_SMMU_EVTQ_PROD);
- writel_relaxed(smmu->evtq.q.llq.cons, smmu->page1 + ARM_SMMU_EVTQ_CONS);
-
- enables |= CR0_EVTQEN;
- ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
- ARM_SMMU_CR0ACK);
- if (ret) {
- dev_err(smmu->dev, "failed to enable event queue\n");
- return ret;
+ /*
+ * Event queue
+ *
+ * Do not enable in a kdump case, as the crashed kernel's CDs and page
+ * tables might be corrupted, triggering event spamming.
+ */
+ if (!is_kdump_kernel()) {
+ writeq_relaxed(smmu->evtq.q.q_base,
+ smmu->base + ARM_SMMU_EVTQ_BASE);
+ writel_relaxed(smmu->evtq.q.llq.prod,
+ smmu->page1 + ARM_SMMU_EVTQ_PROD);
+ writel_relaxed(smmu->evtq.q.llq.cons,
+ smmu->page1 + ARM_SMMU_EVTQ_CONS);
+
+ enables |= CR0_EVTQEN;
+ ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
+ ARM_SMMU_CR0ACK);
+ if (ret) {
+ dev_err(smmu->dev, "failed to enable event queue\n");
+ return ret;
+ }
}

- /* PRI queue */
- if (smmu->features & ARM_SMMU_FEAT_PRI) {
+ /*
+ * PRI queue
+ *
+ * Do not enable in a kdump case, as we cannot serve page requests.
+ */
+ if (!is_kdump_kernel() && (smmu->features & ARM_SMMU_FEAT_PRI)) {
writeq_relaxed(smmu->priq.q.q_base,
smmu->base + ARM_SMMU_PRIQ_BASE);
writel_relaxed(smmu->priq.q.llq.prod,
@@ -5165,9 +5198,6 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
return ret;
}

- if (is_kdump_kernel())
- enables &= ~(CR0_EVTQEN | CR0_PRIQEN);
-
/* Enable the SMMU interface */
enables |= CR0_SMMUEN;
ret = arm_smmu_write_reg_sync(smmu, enables, ARM_SMMU_CR0,
--
2.43.0