drm/amdgpu: use ring/hash for fault handling on GMC9 v3

Further testing showed that the idea with the chash doesn't work as expected.
Especially we can't predict when we can remove the entries from the hash again.

So replace the chash with a ring buffer/hash mix where entries in the container
age automatically based on their timestamp.

v2: use ring buffer / hash mix
v3: check the timeout to make sure all entries age

Signed-off-by: Christian König <[e-mail]>
Reviewed-by: Felix Kuehling <[e-mail]> (v2)
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.c

···
 	dev_info(adev->dev, "AGP: %lluM 0x%016llX - 0x%016llX\n",
 			mc->agp_size >> 20, mc->agp_start, mc->agp_end);
 }
+
+/**
+ * amdgpu_gmc_filter_faults - filter VM faults
+ *
+ * @adev: amdgpu device structure
+ * @addr: address of the VM fault
+ * @pasid: PASID of the process causing the fault
+ * @timestamp: timestamp of the fault
+ *
+ * Returns:
+ * True if the fault was filtered and should not be processed further.
+ * False if the fault is a new one and needs to be handled.
+ */
+bool amdgpu_gmc_filter_faults(struct amdgpu_device *adev, uint64_t addr,
+			      uint16_t pasid, uint64_t timestamp)
+{
+	struct amdgpu_gmc *gmc = &adev->gmc;
+
+	uint64_t stamp, key = addr << 4 | pasid;
+	struct amdgpu_gmc_fault *fault;
+	uint32_t hash;
+
+	/* If we don't have space left in the ring buffer return immediately */
+	stamp = max(timestamp, AMDGPU_GMC_FAULT_TIMEOUT + 1) -
+		AMDGPU_GMC_FAULT_TIMEOUT;
+	if (gmc->fault_ring[gmc->last_fault].timestamp >= stamp)
+		return true;
+
+	/* Try to find the fault in the hash */
+	hash = hash_64(key, AMDGPU_GMC_FAULT_HASH_ORDER);
+	fault = &gmc->fault_ring[gmc->fault_hash[hash].idx];
+	while (fault->timestamp >= stamp) {
+		uint64_t tmp;
+
+		if (fault->key == key)
+			return true;
+
+		tmp = fault->timestamp;
+		fault = &gmc->fault_ring[fault->next];
+
+		/* Check if the entry was reused */
+		if (fault->timestamp >= tmp)
+			break;
+	}
+
+	/* Add the fault to the ring */
+	fault = &gmc->fault_ring[gmc->last_fault];
+	fault->key = key;
+	fault->timestamp = timestamp;
+
+	/* And update the hash */
+	fault->next = gmc->fault_hash[hash].idx;
+	gmc->fault_hash[hash].idx = gmc->last_fault++;
+	return false;
+}

drivers/gpu/drm/amd/amdgpu/amdgpu_gmc.h

···
  */
 #define AMDGPU_GMC_HOLE_MASK	0x0000ffffffffffffULL
 
+/*
+ * Ring size as power of two for the log of recent faults.
+ */
+#define AMDGPU_GMC_FAULT_RING_ORDER	8
+#define AMDGPU_GMC_FAULT_RING_SIZE	(1 << AMDGPU_GMC_FAULT_RING_ORDER)
+
+/*
+ * Hash size as power of two for the log of recent faults
+ */
+#define AMDGPU_GMC_FAULT_HASH_ORDER	8
+#define AMDGPU_GMC_FAULT_HASH_SIZE	(1 << AMDGPU_GMC_FAULT_HASH_ORDER)
+
+/*
+ * Number of IH timestamp ticks until a fault is considered handled
+ */
+#define AMDGPU_GMC_FAULT_TIMEOUT	5000ULL
+
 struct firmware;
+
+/*
+ * GMC page fault information
+ */
+struct amdgpu_gmc_fault {
+	uint64_t	timestamp;
+	uint64_t	next:AMDGPU_GMC_FAULT_RING_ORDER;
+	uint64_t	key:52;
+};
 
 /*
  * VMHUB structures, functions & helpers
···
 	struct kfd_vm_fault_info *vm_fault_info;
 	atomic_t		vm_fault_info_updated;
 
+	struct amdgpu_gmc_fault	fault_ring[AMDGPU_GMC_FAULT_RING_SIZE];
+	struct {
+		uint64_t	idx:AMDGPU_GMC_FAULT_RING_ORDER;
+	} fault_hash[AMDGPU_GMC_FAULT_HASH_SIZE];
+	uint64_t		last_fault:AMDGPU_GMC_FAULT_RING_ORDER;
+
 	const struct amdgpu_gmc_funcs	*gmc_funcs;
 
 	struct amdgpu_xgmi xgmi;
···
 			      struct amdgpu_gmc *mc);
 void amdgpu_gmc_agp_location(struct amdgpu_device *adev,
 			     struct amdgpu_gmc *mc);
+bool amdgpu_gmc_filter_faults(struct amdgpu_device *adev, uint64_t addr,
+			      uint16_t pasid, uint64_t timestamp);
 
 #endif

drivers/gpu/drm/amd/amdgpu/gmc_v9_0.c

···
 	return 0;
 }
 
-/**
- * vega10_ih_prescreen_iv - prescreen an interrupt vector
- *
- * @adev: amdgpu_device pointer
- *
- * Returns true if the interrupt vector should be further processed.
- */
-static bool gmc_v9_0_prescreen_iv(struct amdgpu_device *adev,
-				  struct amdgpu_iv_entry *entry,
-				  uint64_t addr)
-{
-	struct amdgpu_vm *vm;
-	u64 key;
-	int r;
-
-	/* No PASID, can't identify faulting process */
-	if (!entry->pasid)
-		return true;
-
-	/* Not a retry fault */
-	if (!(entry->src_data[1] & 0x80))
-		return true;
-
-	/* Track retry faults in per-VM fault FIFO. */
-	spin_lock(&adev->vm_manager.pasid_lock);
-	vm = idr_find(&adev->vm_manager.pasid_idr, entry->pasid);
-	if (!vm) {
-		/* VM not found, process it normally */
-		spin_unlock(&adev->vm_manager.pasid_lock);
-		return true;
-	}
-
-	key = AMDGPU_VM_FAULT(entry->pasid, addr);
-	r = amdgpu_vm_add_fault(vm->fault_hash, key);
-
-	/* Hash table is full or the fault is already being processed,
-	 * ignore further page faults
-	 */
-	if (r != 0) {
-		spin_unlock(&adev->vm_manager.pasid_lock);
-		return false;
-	}
-	/* No locking required with single writer and single reader */
-	r = kfifo_put(&vm->faults, key);
-	if (!r) {
-		/* FIFO is full. Ignore it until there is space */
-		amdgpu_vm_clear_fault(vm->fault_hash, key);
-		spin_unlock(&adev->vm_manager.pasid_lock);
-		return false;
-	}
-
-	spin_unlock(&adev->vm_manager.pasid_lock);
-	/* It's the first fault for this address, process it normally */
-	return true;
-}
-
 static int gmc_v9_0_process_interrupt(struct amdgpu_device *adev,
 				struct amdgpu_irq_src *source,
 				struct amdgpu_iv_entry *entry)
···
 	addr = (u64)entry->src_data[0] << 12;
 	addr |= ((u64)entry->src_data[1] & 0xf) << 44;
 
-	if (!gmc_v9_0_prescreen_iv(adev, entry, addr))
+	if (retry_fault && amdgpu_gmc_filter_faults(adev, addr, entry->pasid,
+						    entry->timestamp))
 		return 1; /* This also prevents sending it to KFD */
 
+	/* If it's the first fault for this address, process it normally */
 	if (!amdgpu_sriov_vf(adev)) {
 		status = RREG32(hub->vm_l2_pro_fault_status);
 		WREG32_P(hub->vm_l2_pro_fault_cntl, 1, ~1);