[PATCH v4 21/26] iommu/arm-smmu-v3: Ratelimit event dump

Jean-Philippe Brucker
2020-02-24T18:25:27Z

When a device or driver misbehaves, it is possible to receive events
much faster than we can print them out. Ratelimit the printing of
events.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
---
During the SVA tests when the device driver didn't properly stop DMA
before unbinding, the event queue thread would almost lock-up the server
with a flood of event 0xa. This patch helped recover from the error.
---
drivers/iommu/arm-smmu-v3.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 28f8583cd47b..6a5987cce03f 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -2243,17 +2243,20 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
struct arm_smmu_device *smmu = dev;
struct arm_smmu_queue *q = &smmu->evtq.q;
struct arm_smmu_ll_queue *llq = &q->llq;
+ static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
+ DEFAULT_RATELIMIT_BURST);
u64 evt[EVTQ_ENT_DWORDS];

do {
while (!queue_remove_raw(q, evt)) {
u8 id = FIELD_GET(EVTQ_0_ID, evt[0]);

- dev_info(smmu->dev, "event 0x%02x received:\n", id);
- for (i = 0; i < ARRAY_SIZE(evt); ++i)
- dev_info(smmu->dev, "\t0x%016llx\n",
- (unsigned long long)evt[i]);
-
+ if (__ratelimit(&rs)) {
+ dev_info(smmu->dev, "event 0x%02x received:\n", id);
+ for (i = 0; i < ARRAY_SIZE(evt); ++i)
+ dev_info(smmu->dev, "\t0x%016llx\n",
+ (unsigned long long)evt[i]);
+ }
}

/*
--
2.25.0