[PATCH v10 03/13] iommu/arm-smmu-v3: Add ARM_SMMU_FEAT_EVTQ for the event queue
From: Nicolin Chen
Date: Sun Aug 30 2026 - 19:19:07 EST
The driver programs and enables the event queue unconditionally, while the
PRI queue has an ARM_SMMU_FEAT_PRI gating each of its touch points. Yet a
kdump kernel wants to leave both of the queues alone, which would take an
is_kdump_kernel() test at every one of those places.
Add an ARM_SMMU_FEAT_EVTQ that the probe always sets, as the event queue is
architecturally mandatory, and gate the queue's allocation, its interrupt
and its CR0 and IRQ_CTRL enables on it, so that a later change can turn the
queue off in a single place.
No functional change intended.
Suggested-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Suggested-by: Robin Murphy <robin.murphy@xxxxxxx>
Assisted-by: Claude:claude-opus-5
Signed-off-by: Nicolin Chen <nicolinc@xxxxxxxxxx>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 79 +++++++++++++--------
2 files changed, 52 insertions(+), 28 deletions(-)
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 fd6f489cfedf2..75e768b3d66d8 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -927,6 +927,7 @@ struct arm_smmu_device {
#define ARM_SMMU_FEAT_BBML2 (1 << 24)
#define ARM_SMMU_FEAT_HAFT (1 << 25)
#define ARM_SMMU_FEAT_DS (1 << 26)
+#define ARM_SMMU_FEAT_EVTQ (1 << 27)
u32 features;
#define ARM_SMMU_OPT_SKIP_PREFETCH (1 << 0)
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 c1d04f84870f6..c776fdd43325d 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2349,7 +2349,8 @@ static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
{
struct arm_smmu_device *smmu = dev;
- arm_smmu_evtq_thread(irq, dev);
+ if (smmu->features & ARM_SMMU_FEAT_EVTQ)
+ arm_smmu_evtq_thread(irq, dev);
if (smmu->features & ARM_SMMU_FEAT_PRI)
arm_smmu_priq_thread(irq, dev);
@@ -2358,7 +2359,12 @@ static irqreturn_t arm_smmu_combined_irq_thread(int irq, void *dev)
static irqreturn_t arm_smmu_combined_irq_handler(int irq, void *dev)
{
- arm_smmu_gerror_handler(irq, dev);
+ struct arm_smmu_device *smmu = dev;
+ irqreturn_t ret = arm_smmu_gerror_handler(irq, dev);
+
+ /* Without either queue, the thread would have nothing to drain */
+ if (!(smmu->features & (ARM_SMMU_FEAT_EVTQ | ARM_SMMU_FEAT_PRI)))
+ return ret;
return IRQ_WAKE_THREAD;
}
@@ -4505,11 +4511,14 @@ static int arm_smmu_init_queues(struct arm_smmu_device *smmu)
return ret;
/* evtq */
- ret = arm_smmu_init_one_queue(smmu, &smmu->evtq.q, smmu->page1,
- ARM_SMMU_EVTQ_PROD, ARM_SMMU_EVTQ_CONS,
- EVTQ_ENT_DWORDS, "evtq");
- if (ret)
- return ret;
+ if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+ ret = arm_smmu_init_one_queue(smmu, &smmu->evtq.q, smmu->page1,
+ ARM_SMMU_EVTQ_PROD,
+ ARM_SMMU_EVTQ_CONS,
+ EVTQ_ENT_DWORDS, "evtq");
+ if (ret)
+ return ret;
+ }
if ((smmu->features & ARM_SMMU_FEAT_SVA) &&
(smmu->features & ARM_SMMU_FEAT_STALLS)) {
@@ -4729,16 +4738,20 @@ static void arm_smmu_setup_unique_irqs(struct arm_smmu_device *smmu)
arm_smmu_setup_msis(smmu);
/* Request interrupt lines */
- irq = smmu->evtq.q.irq;
- if (irq) {
- ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
- arm_smmu_evtq_thread,
- IRQF_ONESHOT,
- "arm-smmu-v3-evtq", smmu);
- if (ret < 0)
- dev_warn(smmu->dev, "failed to enable evtq irq\n");
- } else {
- dev_warn(smmu->dev, "no evtq irq - events will not be reported!\n");
+ if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+ irq = smmu->evtq.q.irq;
+ if (irq) {
+ ret = devm_request_threaded_irq(smmu->dev, irq, NULL,
+ arm_smmu_evtq_thread,
+ IRQF_ONESHOT,
+ "arm-smmu-v3-evtq", smmu);
+ if (ret < 0)
+ dev_warn(smmu->dev,
+ "failed to enable evtq irq\n");
+ } else {
+ dev_warn(smmu->dev,
+ "no evtq irq - events will not be reported!\n");
+ }
}
irq = smmu->gerr_irq;
@@ -4771,7 +4784,7 @@ 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;
/* Disable IRQs first */
ret = arm_smmu_write_reg_sync(smmu, 0, ARM_SMMU_IRQ_CTRL,
@@ -4797,6 +4810,8 @@ static int arm_smmu_setup_irqs(struct arm_smmu_device *smmu)
} else
arm_smmu_setup_unique_irqs(smmu);
+ if (smmu->features & ARM_SMMU_FEAT_EVTQ)
+ irqen_flags |= IRQ_CTRL_EVTQ_IRQEN;
if (smmu->features & ARM_SMMU_FEAT_PRI)
irqen_flags |= IRQ_CTRL_PRIQ_IRQEN;
@@ -4915,16 +4930,21 @@ static int arm_smmu_device_reset(struct arm_smmu_device *smmu)
smmu, arm_smmu_make_cmd_op(CMDQ_OP_TLBI_NSNH_ALL));
/* 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;
+ if (smmu->features & ARM_SMMU_FEAT_EVTQ) {
+ 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 */
@@ -5063,6 +5083,9 @@ static int arm_smmu_device_hw_probe(struct arm_smmu_device *smmu)
u32 reg;
bool coherent = smmu->features & ARM_SMMU_FEAT_COHERENCY;
+ /* The event queue is architecturally mandatory, unlike the PRI queue */
+ smmu->features |= ARM_SMMU_FEAT_EVTQ;
+
/* IDR0 */
reg = readl_relaxed(smmu->base + ARM_SMMU_IDR0);
--
2.43.0