iommu/arm-smmu-v3: Ratelimit event dump

maillist inclusion
category: feature
bugzilla: 51855
CVE: NA

Reference: https://jpbrucker.net/git/linux/commit/?h=sva/2021-03-01&id=b61d8bac171c221b3d14c03eba78338bfbbb8825

---------------------------------------------

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: NJean-Philippe Brucker <jean-philippe@linaro.org>
Signed-off-by: NLijun Fang <fanglijun3@huawei.com>
Reviewed-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c

@@ -1546,6 +1546,8 @@ 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 {
@@ -1553,7 +1555,7 @@ static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
 			u8 id = FIELD_GET(EVTQ_0_ID, evt[0]);
 
 			ret = arm_smmu_handle_evt(smmu, evt);
-			if (!ret)
+			if (!ret || !__ratelimit(&rs))
 				continue;
 
 			dev_info(smmu->dev, "event 0x%02x received:\n", id);