Re: [PATCH v7 18/23] iommu/smmuv3: Report non recoverable faults

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On 08/04/2019 13:19, Eric Auger wrote:
When a stage 1 related fault event is read from the event queue,
let's propagate it to potential external fault listeners, ie. users
who registered a fault handler.

Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>

---
v4 -> v5:
- s/IOMMU_FAULT_PERM_INST/IOMMU_FAULT_PERM_EXEC
---
  drivers/iommu/arm-smmu-v3.c | 169 +++++++++++++++++++++++++++++++++---
  1 file changed, 158 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
index 8044445bc32a..1fd320788dcb 100644
--- a/drivers/iommu/arm-smmu-v3.c
+++ b/drivers/iommu/arm-smmu-v3.c
@@ -167,6 +167,26 @@
  #define ARM_SMMU_PRIQ_IRQ_CFG1		0xd8
  #define ARM_SMMU_PRIQ_IRQ_CFG2		0xdc
+/* Events */
+#define ARM_SMMU_EVT_F_UUT		0x01
+#define ARM_SMMU_EVT_C_BAD_STREAMID	0x02
+#define ARM_SMMU_EVT_F_STE_FETCH	0x03
+#define ARM_SMMU_EVT_C_BAD_STE		0x04
+#define ARM_SMMU_EVT_F_BAD_ATS_TREQ	0x05
+#define ARM_SMMU_EVT_F_STREAM_DISABLED	0x06
+#define ARM_SMMU_EVT_F_TRANSL_FORBIDDEN	0x07
+#define ARM_SMMU_EVT_C_BAD_SUBSTREAMID	0x08
+#define ARM_SMMU_EVT_F_CD_FETCH		0x09
+#define ARM_SMMU_EVT_C_BAD_CD		0x0a
+#define ARM_SMMU_EVT_F_WALK_EABT	0x0b
+#define ARM_SMMU_EVT_F_TRANSLATION	0x10
+#define ARM_SMMU_EVT_F_ADDR_SIZE	0x11
+#define ARM_SMMU_EVT_F_ACCESS		0x12
+#define ARM_SMMU_EVT_F_PERMISSION	0x13
+#define ARM_SMMU_EVT_F_TLB_CONFLICT	0x20
+#define ARM_SMMU_EVT_F_CFG_CONFLICT	0x21
+#define ARM_SMMU_EVT_E_PAGE_REQUEST	0x24
+
  /* Common MSI config fields */
  #define MSI_CFG0_ADDR_MASK		GENMASK_ULL(51, 2)
  #define MSI_CFG2_SH			GENMASK(5, 4)
@@ -332,6 +352,15 @@
  #define EVTQ_MAX_SZ_SHIFT		7
#define EVTQ_0_ID GENMASK_ULL(7, 0)
+#define EVTQ_0_SSV			GENMASK_ULL(11, 11)
+#define EVTQ_0_SUBSTREAMID		GENMASK_ULL(31, 12)
+#define EVTQ_0_STREAMID			GENMASK_ULL(63, 32)
+#define EVTQ_1_PNU			GENMASK_ULL(33, 33)
+#define EVTQ_1_IND			GENMASK_ULL(34, 34)
+#define EVTQ_1_RNW			GENMASK_ULL(35, 35)
+#define EVTQ_1_S2			GENMASK_ULL(39, 39)
+#define EVTQ_1_CLASS			GENMASK_ULL(40, 41)
+#define EVTQ_3_FETCH_ADDR		GENMASK_ULL(51, 3)
/* PRI queue */
  #define PRIQ_ENT_DWORDS			2
@@ -639,6 +668,64 @@ struct arm_smmu_domain {
  	spinlock_t			devices_lock;
  };
+/* fault propagation */
+
+#define IOMMU_FAULT_F_FIELDS	(IOMMU_FAULT_UNRECOV_PASID_VALID | \
+				 IOMMU_FAULT_UNRECOV_PERM_VALID | \
+				 IOMMU_FAULT_UNRECOV_ADDR_VALID)
+
+struct arm_smmu_fault_propagation_data {
+	enum iommu_fault_reason reason;
+	bool s1_check;
+	u32 fields; /* IOMMU_FAULT_UNRECOV_*_VALID bits */
+};
+
+/*
+ * Describes how SMMU faults translate into generic IOMMU faults
+ * and if they need to be reported externally
+ */
+static const struct arm_smmu_fault_propagation_data fault_propagation[] = {
+[ARM_SMMU_EVT_F_UUT]			= { },
+[ARM_SMMU_EVT_C_BAD_STREAMID]		= { },
+[ARM_SMMU_EVT_F_STE_FETCH]		= { },
+[ARM_SMMU_EVT_C_BAD_STE]		= { },
+[ARM_SMMU_EVT_F_BAD_ATS_TREQ]		= { },
+[ARM_SMMU_EVT_F_STREAM_DISABLED]	= { },
+[ARM_SMMU_EVT_F_TRANSL_FORBIDDEN]	= { },
+[ARM_SMMU_EVT_C_BAD_SUBSTREAMID]	= {IOMMU_FAULT_REASON_PASID_INVALID,
+					   false,
+					   IOMMU_FAULT_UNRECOV_PASID_VALID
+					  },
+[ARM_SMMU_EVT_F_CD_FETCH]		= {IOMMU_FAULT_REASON_PASID_FETCH,
+					   false,
+					   IOMMU_FAULT_UNRECOV_PASID_VALID |

It doesn't make sense to presume validity here, or in any of the faults below...

+					   IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID
+					  },
+[ARM_SMMU_EVT_C_BAD_CD]			= {IOMMU_FAULT_REASON_BAD_PASID_ENTRY,
+					   false,
+					   IOMMU_FAULT_UNRECOV_PASID_VALID
+					  },
+[ARM_SMMU_EVT_F_WALK_EABT]		= {IOMMU_FAULT_REASON_WALK_EABT, true,
+					   IOMMU_FAULT_F_FIELDS |
+					   IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID
+					  },
+[ARM_SMMU_EVT_F_TRANSLATION]		= {IOMMU_FAULT_REASON_PTE_FETCH, true,
+					   IOMMU_FAULT_F_FIELDS
+					  },
+[ARM_SMMU_EVT_F_ADDR_SIZE]		= {IOMMU_FAULT_REASON_OOR_ADDRESS, true,
+					   IOMMU_FAULT_F_FIELDS
+					  },
+[ARM_SMMU_EVT_F_ACCESS]			= {IOMMU_FAULT_REASON_ACCESS, true,
+					   IOMMU_FAULT_F_FIELDS
+					  },
+[ARM_SMMU_EVT_F_PERMISSION]		= {IOMMU_FAULT_REASON_PERMISSION, true,
+					   IOMMU_FAULT_F_FIELDS
+					  },
+[ARM_SMMU_EVT_F_TLB_CONFLICT]		= { },
+[ARM_SMMU_EVT_F_CFG_CONFLICT]		= { },
+[ARM_SMMU_EVT_E_PAGE_REQUEST]		= { },
+};
+
  struct arm_smmu_option_prop {
  	u32 opt;
  	const char *prop;
@@ -1258,7 +1345,6 @@ static int arm_smmu_init_l2_strtab(struct arm_smmu_device *smmu, u32 sid)
  	return 0;
  }
-__maybe_unused
  static struct arm_smmu_master_data *
  arm_smmu_find_master(struct arm_smmu_device *smmu, u32 sid)
  {
@@ -1284,24 +1370,85 @@ arm_smmu_find_master(struct arm_smmu_device *smmu, u32 sid)
  	return master;
  }
+/* Populates the record fields according to the input SMMU event */
+static bool arm_smmu_transcode_fault(u64 *evt, u8 type,
+				     struct iommu_fault_unrecoverable *record)
+{
+	const struct arm_smmu_fault_propagation_data *data;
+	u32 fields;
+
+	if (type >= ARRAY_SIZE(fault_propagation))
+		return false;
+
+	data = &fault_propagation[type];
+	if (!data->reason)
+		return false;
+
+	fields = data->fields;
+
+	if (data->s1_check & FIELD_GET(EVTQ_1_S2, evt[1]))
+		return false; /* S2 related fault, don't propagate */
+
+	if (fields & IOMMU_FAULT_UNRECOV_PASID_VALID) {
+		if (FIELD_GET(EVTQ_0_SSV, evt[0]))
+			record->pasid = FIELD_GET(EVTQ_0_SUBSTREAMID, evt[0]);
+		else
+			fields &= ~IOMMU_FAULT_UNRECOV_PASID_VALID;

...because this logic then breaks for C_BAD_SUBSTREAMID, which ends up coming out of here *without* reporting the offending PASID.

+	}
+	if (fields & IOMMU_FAULT_UNRECOV_PERM_VALID) {
+		if (!FIELD_GET(EVTQ_1_RNW, evt[1]))
+			record->perm |= IOMMU_FAULT_PERM_WRITE;
+		if (FIELD_GET(EVTQ_1_PNU, evt[1]))
+			record->perm |= IOMMU_FAULT_PERM_PRIV;
+		if (FIELD_GET(EVTQ_1_IND, evt[1]))
+			record->perm |= IOMMU_FAULT_PERM_EXEC;
+	}
+	if (fields & IOMMU_FAULT_UNRECOV_ADDR_VALID)
+		record->addr = evt[2];
+
+	if (fields & IOMMU_FAULT_UNRECOV_FETCH_ADDR_VALID)
+		record->fetch_addr = FIELD_GET(EVTQ_3_FETCH_ADDR, evt[3]);
+
+	record->flags = fields;
+	return true;
+}
+
+static void arm_smmu_report_event(struct arm_smmu_device *smmu, u64 *evt)
+{
+	u32 sid = FIELD_GET(EVTQ_0_STREAMID, evt[0]);
+	u8 type = FIELD_GET(EVTQ_0_ID, evt[0]);
+	struct arm_smmu_master_data *master;
+	struct iommu_fault_event event = {};
+	int i;
+
+	master = arm_smmu_find_master(smmu, sid);
+	if (WARN_ON(!master))
+		return;

NAK. If I'm getting global faults like C_BAD_STE where a device almost certainly *isn't* configured (because hey, we would have initialised its STEs if we knew), then I sure as hell want to see the actual faults. Spamming a constant stream of stack traces *instead* of showing them is worse than useless.

+
+	event.fault.type = IOMMU_FAULT_DMA_UNRECOV;
+
+	if (arm_smmu_transcode_fault(evt, type, &event.fault.event)) {
+		iommu_report_device_fault(master->dev, &event);
+		return;

And again, the vast majority of the time, there won't be a fault handler registered, so unconditionally suppressing the most common and useful stuff like translation and permission faults is very much not OK.

Robin.

+	}
+
+	dev_info(smmu->dev, "event 0x%02x received:\n", type);
+	for (i = 0; i < EVTQ_ENT_DWORDS; ++i) {
+		dev_info(smmu->dev, "\t0x%016llx\n",
+			 (unsigned long long)evt[i]);
+	}
+}
+
  /* IRQ and event handlers */
  static irqreturn_t arm_smmu_evtq_thread(int irq, void *dev)
  {
-	int i;
  	struct arm_smmu_device *smmu = dev;
  	struct arm_smmu_queue *q = &smmu->evtq.q;
  	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]);
-
-		}
+		while (!queue_remove_raw(q, evt))
+			arm_smmu_report_event(smmu, evt);
/*
  		 * Not much we can do on overflow, so scream and pretend we're

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