KVM: SEV: Do cache maintenance on the source VM during intra-host migrationgrafted

Manually perform cache maintenance on the source VM during intra-host
migration to ensure no stale data is left in CPU caches after the VM is
destroyed.  Because the source VM is "converted" to a non-SEV VM, KVM's
memory reclaim flows won't trigger cache maintenance, e.g. when all guest
memory is reclaimed in response to detaching from the mmu_notifier.

Note, relying on the destination VM to do cache maintenance isn't an option
as KVM doesn't require identical guest memory configurations, i.e. the
source VM may have access to memory that the destination VM does not.
Enforcing equivalent memory configurations is infeasible, as it would
require a *deep* comparison of memslots, e.g. to verify that not only are
the memslot identical, but what the memslots point at is also identical.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Cc: stable@vger.kernel.org
Reported-by: Stefan Teodorescu <fane@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20260923163721.1584779-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 890 insertions, 0 deletions

diff --git a/lib/test_rhashtable.c b/lib/test_rhashtable.c
new file mode 100644
index 000000000..2f922b63d
--- /dev/null
+++ b/lib/test_rhashtable.c
@@ -0,0 +1,890 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Resizable, Scalable, Concurrent Hash Table
+ *
+ * Copyright (c) 2014-2015 Thomas Graf <tgraf@suug.ch>
+ * Copyright (c) 2008-2014 Patrick McHardy <kaber@trash.net>
+ */
+
+/**************************************************************************
+ * Self Test
+ **************************************************************************/
+
+#include <linux/init.h>
+#include <linux/jhash.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/module.h>
+#include <linux/rcupdate.h>
+#include <linux/rcupdate_wait.h>
+#include <linux/rhashtable.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/random.h>
+#include <linux/vmalloc.h>
+#include <linux/wait.h>
+
+#define MAX_ENTRIES	1000000
+#define TEST_INSERT_FAIL INT_MAX
+
+static int parm_entries = 50000;
+module_param(parm_entries, int, 0);
+MODULE_PARM_DESC(parm_entries, "Number of entries to add (default: 50000)");
+
+static int runs = 4;
+module_param(runs, int, 0);
+MODULE_PARM_DESC(runs, "Number of test runs per variant (default: 4)");
+
+static int max_size = 0;
+module_param(max_size, int, 0);
+MODULE_PARM_DESC(max_size, "Maximum table size (default: calculated)");
+
+static bool shrinking = false;
+module_param(shrinking, bool, 0);
+MODULE_PARM_DESC(shrinking, "Enable automatic shrinking (default: off)");
+
+static int size = 8;
+module_param(size, int, 0);
+MODULE_PARM_DESC(size, "Initial size hint of table (default: 8)");
+
+static int tcount = 10;
+module_param(tcount, int, 0);
+MODULE_PARM_DESC(tcount, "Number of threads to spawn (default: 10)");
+
+static bool enomem_retry = false;
+module_param(enomem_retry, bool, 0);
+MODULE_PARM_DESC(enomem_retry, "Retry insert even if -ENOMEM was returned (default: off)");
+
+struct test_obj_val {
+	int	id;
+	int	tid;
+};
+
+struct test_obj {
+	struct test_obj_val	value;
+	struct rhash_head	node;
+};
+
+struct test_obj_rhl {
+	struct test_obj_val	value;
+	struct rhlist_head	list_node;
+};
+
+struct thread_data {
+	unsigned int entries;
+	int id;
+	struct task_struct *task;
+	struct test_obj *objs;
+};
+
+static u32 my_hashfn(const void *data, u32 len, u32 seed)
+{
+	const struct test_obj_rhl *obj = data;
+
+	return (obj->value.id % 10);
+}
+
+static int my_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct test_obj_rhl *test_obj = obj;
+	const struct test_obj_val *val = arg->key;
+
+	return test_obj->value.id - val->id;
+}
+
+static struct rhashtable_params test_rht_params = {
+	.head_offset = offsetof(struct test_obj, node),
+	.key_offset = offsetof(struct test_obj, value),
+	.key_len = sizeof(struct test_obj_val),
+	.hashfn = jhash,
+};
+
+static struct rhashtable_params test_rht_params_dup = {
+	.head_offset = offsetof(struct test_obj_rhl, list_node),
+	.key_offset = offsetof(struct test_obj_rhl, value),
+	.key_len = sizeof(struct test_obj_val),
+	.hashfn = jhash,
+	.obj_hashfn = my_hashfn,
+	.obj_cmpfn = my_cmpfn,
+	.nelem_hint = 128,
+	.automatic_shrinking = false,
+};
+
+static atomic_t startup_count;
+static DECLARE_WAIT_QUEUE_HEAD(startup_wait);
+
+static int insert_retry(struct rhashtable *ht, struct test_obj *obj,
+                        const struct rhashtable_params params)
+{
+	int err, retries = -1, enomem_retries = 0;
+
+	do {
+		retries++;
+		cond_resched();
+		err = rhashtable_insert_fast(ht, &obj->node, params);
+		if (err == -ENOMEM && enomem_retry) {
+			enomem_retries++;
+			err = -EBUSY;
+		}
+	} while (err == -EBUSY);
+
+	if (enomem_retries)
+		pr_info(" %u insertions retried after -ENOMEM\n",
+			enomem_retries);
+
+	return err ? : retries;
+}
+
+static int __init test_rht_lookup(struct rhashtable *ht, struct test_obj *array,
+				  unsigned int entries)
+{
+	unsigned int i;
+
+	for (i = 0; i < entries; i++) {
+		struct test_obj *obj;
+		bool expected = !(i % 2);
+		struct test_obj_val key = {
+			.id = i,
+		};
+
+		if (array[i / 2].value.id == TEST_INSERT_FAIL)
+			expected = false;
+
+		obj = rhashtable_lookup_fast(ht, &key, test_rht_params);
+
+		if (expected && !obj) {
+			pr_warn("Test failed: Could not find key %u\n", key.id);
+			return -ENOENT;
+		} else if (!expected && obj) {
+			pr_warn("Test failed: Unexpected entry found for key %u\n",
+				key.id);
+			return -EEXIST;
+		} else if (expected && obj) {
+			if (obj->value.id != i) {
+				pr_warn("Test failed: Lookup value mismatch %u!=%u\n",
+					obj->value.id, i);
+				return -EINVAL;
+			}
+		}
+
+		cond_resched_rcu();
+	}
+
+	return 0;
+}
+
+static void test_bucket_stats(struct rhashtable *ht, unsigned int entries)
+{
+	unsigned int total = 0, chain_len = 0;
+	struct rhashtable_iter hti;
+	struct rhash_head *pos;
+
+	rhashtable_walk_enter(ht, &hti);
+	rhashtable_walk_start(&hti);
+
+	while ((pos = rhashtable_walk_next(&hti))) {
+		if (PTR_ERR(pos) == -EAGAIN) {
+			pr_info("Info: encountered resize\n");
+			chain_len++;
+			continue;
+		} else if (IS_ERR(pos)) {
+			pr_warn("Test failed: rhashtable_walk_next() error: %ld\n",
+				PTR_ERR(pos));
+			break;
+		}
+
+		total++;
+	}
+
+	rhashtable_walk_stop(&hti);
+	rhashtable_walk_exit(&hti);
+
+	pr_info("  Traversal complete: counted=%u, nelems=%u, entries=%d, table-jumps=%u\n",
+		total, atomic_read(&ht->nelems), entries, chain_len);
+
+	if (total != atomic_read(&ht->nelems) || total != entries)
+		pr_warn("Test failed: Total count mismatch ^^^");
+}
+
+static s64 __init test_rhashtable(struct rhashtable *ht, struct test_obj *array,
+				  unsigned int entries)
+{
+	struct test_obj *obj;
+	int err;
+	unsigned int i, insert_retries = 0;
+	s64 start, end;
+
+	/*
+	 * Insertion Test:
+	 * Insert entries into table with all keys even numbers
+	 */
+	pr_info("  Adding %d keys\n", entries);
+	start = ktime_get_ns();
+	for (i = 0; i < entries; i++) {
+		struct test_obj *obj = &array[i];
+
+		obj->value.id = i * 2;
+		err = insert_retry(ht, obj, test_rht_params);
+		if (err > 0)
+			insert_retries += err;
+		else if (err)
+			return err;
+	}
+
+	if (insert_retries)
+		pr_info("  %u insertions retried due to memory pressure\n",
+			insert_retries);
+
+	test_bucket_stats(ht, entries);
+	rcu_read_lock();
+	test_rht_lookup(ht, array, entries);
+	rcu_read_unlock();
+
+	test_bucket_stats(ht, entries);
+
+	pr_info("  Deleting %d keys\n", entries);
+	for (i = 0; i < entries; i++) {
+		struct test_obj_val key = {
+			.id = i * 2,
+		};
+
+		if (array[i].value.id != TEST_INSERT_FAIL) {
+			obj = rhashtable_lookup_fast(ht, &key, test_rht_params);
+			BUG_ON(!obj);
+
+			rhashtable_remove_fast(ht, &obj->node, test_rht_params);
+		}
+
+		cond_resched();
+	}
+
+	end = ktime_get_ns();
+	pr_info("  Duration of test: %lld ns\n", end - start);
+
+	return end - start;
+}
+
+static struct rhashtable ht;
+static struct rhltable rhlt;
+
+static int __init test_rhltable(unsigned int entries)
+{
+	struct test_obj_rhl *rhl_test_objects;
+	unsigned long *obj_in_table;
+	unsigned int i, j, k;
+	int ret, err;
+
+	if (entries == 0)
+		entries = 1;
+
+	rhl_test_objects = vzalloc(array_size(entries,
+					      sizeof(*rhl_test_objects)));
+	if (!rhl_test_objects)
+		return -ENOMEM;
+
+	ret = -ENOMEM;
+	obj_in_table = vzalloc(array_size(sizeof(unsigned long),
+					  BITS_TO_LONGS(entries)));
+	if (!obj_in_table)
+		goto out_free;
+
+	err = rhltable_init(&rhlt, &test_rht_params);
+	if (WARN_ON(err))
+		goto out_free;
+
+	k = get_random_u32();
+	ret = 0;
+	for (i = 0; i < entries; i++) {
+		rhl_test_objects[i].value.id = k;
+		err = rhltable_insert(&rhlt, &rhl_test_objects[i].list_node,
+				      test_rht_params);
+		if (WARN(err, "error %d on element %d\n", err, i))
+			break;
+		if (err == 0)
+			set_bit(i, obj_in_table);
+	}
+
+	if (err)
+		ret = err;
+
+	pr_info("test %d add/delete pairs into rhlist\n", entries);
+	for (i = 0; i < entries; i++) {
+		struct rhlist_head *h, *pos;
+		struct test_obj_rhl *obj;
+		struct test_obj_val key = {
+			.id = k,
+		};
+		bool found;
+
+		rcu_read_lock();
+		h = rhltable_lookup(&rhlt, &key, test_rht_params);
+		if (WARN(!h, "key not found during iteration %d of %d", i, entries)) {
+			rcu_read_unlock();
+			break;
+		}
+
+		if (i) {
+			j = i - 1;
+			rhl_for_each_entry_rcu(obj, pos, h, list_node) {
+				if (WARN(pos == &rhl_test_objects[j].list_node, "old element found, should be gone"))
+					break;
+			}
+		}
+
+		cond_resched_rcu();
+
+		found = false;
+
+		rhl_for_each_entry_rcu(obj, pos, h, list_node) {
+			if (pos == &rhl_test_objects[i].list_node) {
+				found = true;
+				break;
+			}
+		}
+
+		rcu_read_unlock();
+
+		if (WARN(!found, "element %d not found", i))
+			break;
+
+		err = rhltable_remove(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+		WARN(err, "rhltable_remove: err %d for iteration %d\n", err, i);
+		if (err == 0)
+			clear_bit(i, obj_in_table);
+	}
+
+	if (ret == 0 && err)
+		ret = err;
+
+	for (i = 0; i < entries; i++) {
+		WARN(test_bit(i, obj_in_table), "elem %d allegedly still present", i);
+
+		err = rhltable_insert(&rhlt, &rhl_test_objects[i].list_node,
+				      test_rht_params);
+		if (WARN(err, "error %d on element %d\n", err, i))
+			break;
+		if (err == 0)
+			set_bit(i, obj_in_table);
+	}
+
+	pr_info("test %d random rhlist add/delete operations\n", entries);
+	for (j = 0; j < entries; j++) {
+		u32 i = get_random_u32_below(entries);
+		u32 prand = get_random_u32_below(4);
+
+		cond_resched();
+
+		err = rhltable_remove(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+		if (test_bit(i, obj_in_table)) {
+			clear_bit(i, obj_in_table);
+			if (WARN(err, "cannot remove element at slot %d", i))
+				continue;
+		} else {
+			if (WARN(err != -ENOENT, "removed non-existent element %d, error %d not %d",
+			     i, err, -ENOENT))
+				continue;
+		}
+
+		if (prand & 1) {
+			err = rhltable_insert(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+			if (err == 0) {
+				if (WARN(test_and_set_bit(i, obj_in_table), "succeeded to insert same object %d", i))
+					continue;
+			} else {
+				if (WARN(!test_bit(i, obj_in_table), "failed to insert object %d", i))
+					continue;
+			}
+		}
+
+		if (prand & 2) {
+			i = get_random_u32_below(entries);
+			if (test_bit(i, obj_in_table)) {
+				err = rhltable_remove(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+				WARN(err, "cannot remove element at slot %d", i);
+				if (err == 0)
+					clear_bit(i, obj_in_table);
+			} else {
+				err = rhltable_insert(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+				WARN(err, "failed to insert object %d", i);
+				if (err == 0)
+					set_bit(i, obj_in_table);
+			}
+		}
+	}
+
+	for (i = 0; i < entries; i++) {
+		cond_resched();
+		err = rhltable_remove(&rhlt, &rhl_test_objects[i].list_node, test_rht_params);
+		if (test_bit(i, obj_in_table)) {
+			if (WARN(err, "cannot remove element at slot %d", i))
+				continue;
+		} else {
+			if (WARN(err != -ENOENT, "removed non-existent element, error %d not %d",
+				 err, -ENOENT))
+				continue;
+		}
+	}
+
+	rhltable_destroy(&rhlt);
+out_free:
+	vfree(rhl_test_objects);
+	vfree(obj_in_table);
+	return ret;
+}
+
+static int __init test_rhashtable_max(struct test_obj *array,
+				      unsigned int entries)
+{
+	unsigned int i;
+	int err;
+
+	test_rht_params.max_size = roundup_pow_of_two(entries / 8);
+	err = rhashtable_init(&ht, &test_rht_params);
+	if (err)
+		return err;
+
+	for (i = 0; i < ht.max_elems; i++) {
+		struct test_obj *obj = &array[i];
+
+		obj->value.id = i * 2;
+		err = insert_retry(&ht, obj, test_rht_params);
+		if (err < 0)
+			return err;
+	}
+
+	err = insert_retry(&ht, &array[ht.max_elems], test_rht_params);
+	if (err == -E2BIG) {
+		err = 0;
+	} else {
+		pr_info("insert element %u should have failed with %d, got %d\n",
+				ht.max_elems, -E2BIG, err);
+		if (err == 0)
+			err = -1;
+	}
+
+	rhashtable_destroy(&ht);
+
+	return err;
+}
+
+static unsigned int __init print_ht(struct rhltable *rhlt)
+{
+	struct rhashtable *ht;
+	const struct bucket_table *tbl;
+	char buff[512] = "";
+	int offset = 0;
+	unsigned int i, cnt = 0;
+
+	ht = &rhlt->ht;
+	/* Take the mutex to avoid RCU warning */
+	mutex_lock(&ht->mutex);
+	tbl = rht_dereference(ht->tbl, ht);
+	for (i = 0; i < tbl->size; i++) {
+		struct rhash_head *pos, *next;
+		struct test_obj_rhl *p;
+
+		pos = rht_ptr_exclusive(tbl->buckets + i);
+		next = !rht_is_a_nulls(pos) ? rht_dereference(pos->next, ht) : NULL;
+
+		if (!rht_is_a_nulls(pos)) {
+			offset += sprintf(buff + offset, "\nbucket[%d] -> ", i);
+		}
+
+		while (!rht_is_a_nulls(pos)) {
+			struct rhlist_head *list = container_of(pos, struct rhlist_head, rhead);
+			offset += sprintf(buff + offset, "[[");
+			do {
+				pos = &list->rhead;
+				list = rht_dereference(list->next, ht);
+				p = rht_obj(ht, pos);
+
+				offset += sprintf(buff + offset, " val %d (tid=%d)%s", p->value.id, p->value.tid,
+					list? ", " : " ");
+				cnt++;
+			} while (list);
+
+			pos = next,
+			next = !rht_is_a_nulls(pos) ?
+				rht_dereference(pos->next, ht) : NULL;
+
+			offset += sprintf(buff + offset, "]]%s", !rht_is_a_nulls(pos) ? " -> " : "");
+		}
+	}
+	printk(KERN_ERR "\n---- ht: ----%s\n-------------\n", buff);
+	mutex_unlock(&ht->mutex);
+
+	return cnt;
+}
+
+static int __init test_insert_dup(struct test_obj_rhl *rhl_test_objects,
+				  int cnt, bool slow)
+{
+	struct rhltable *rhlt;
+	unsigned int i, ret;
+	const char *key;
+	int err = 0;
+
+	rhlt = kmalloc_obj(*rhlt);
+	if (WARN_ON(!rhlt))
+		return -EINVAL;
+
+	err = rhltable_init(rhlt, &test_rht_params_dup);
+	if (WARN_ON(err)) {
+		kfree(rhlt);
+		return err;
+	}
+
+	for (i = 0; i < cnt; i++) {
+		rhl_test_objects[i].value.tid = i;
+		key = rht_obj(&rhlt->ht, &rhl_test_objects[i].list_node.rhead);
+		key += test_rht_params_dup.key_offset;
+
+		if (slow) {
+			err = PTR_ERR(rhashtable_insert_slow(&rhlt->ht, key,
+							     &rhl_test_objects[i].list_node.rhead));
+			if (err == -EAGAIN)
+				err = 0;
+		} else
+			err = rhltable_insert(rhlt,
+					      &rhl_test_objects[i].list_node,
+					      test_rht_params_dup);
+		if (WARN(err, "error %d on element %d/%d (%s)\n", err, i, cnt, slow? "slow" : "fast"))
+			goto skip_print;
+	}
+
+	ret = print_ht(rhlt);
+	WARN(ret != cnt, "missing rhltable elements (%d != %d, %s)\n", ret, cnt, slow? "slow" : "fast");
+
+skip_print:
+	rhltable_destroy(rhlt);
+	kfree(rhlt);
+
+	return 0;
+}
+
+static int __init test_insert_duplicates_run(void)
+{
+	struct test_obj_rhl rhl_test_objects[3] = {};
+
+	pr_info("test inserting duplicates\n");
+
+	/* two different values that map to same bucket */
+	rhl_test_objects[0].value.id = 1;
+	rhl_test_objects[1].value.id = 21;
+
+	/* and another duplicate with same as [0] value
+	 * which will be second on the bucket list */
+	rhl_test_objects[2].value.id = rhl_test_objects[0].value.id;
+
+	test_insert_dup(rhl_test_objects, 2, false);
+	test_insert_dup(rhl_test_objects, 3, false);
+	test_insert_dup(rhl_test_objects, 2, true);
+	test_insert_dup(rhl_test_objects, 3, true);
+
+	return 0;
+}
+
+static int thread_lookup_test(struct thread_data *tdata)
+{
+	unsigned int entries = tdata->entries;
+	int i, err = 0;
+
+	for (i = 0; i < entries; i++) {
+		struct test_obj *obj;
+		struct test_obj_val key = {
+			.id = i,
+			.tid = tdata->id,
+		};
+
+		obj = rhashtable_lookup_fast(&ht, &key, test_rht_params);
+		if (obj && (tdata->objs[i].value.id == TEST_INSERT_FAIL)) {
+			pr_err("  found unexpected object %d-%d\n", key.tid, key.id);
+			err++;
+		} else if (!obj && (tdata->objs[i].value.id != TEST_INSERT_FAIL)) {
+			pr_err("  object %d-%d not found!\n", key.tid, key.id);
+			err++;
+		} else if (obj && memcmp(&obj->value, &key, sizeof(key))) {
+			pr_err("  wrong object returned (got %d-%d, expected %d-%d)\n",
+			       obj->value.tid, obj->value.id, key.tid, key.id);
+			err++;
+		}
+
+		cond_resched();
+	}
+	return err;
+}
+
+static int threadfunc(void *data)
+{
+	int i, step, err = 0, insert_retries = 0;
+	struct thread_data *tdata = data;
+
+	if (atomic_dec_and_test(&startup_count))
+		wake_up(&startup_wait);
+	if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == -1)) {
+		pr_err("  thread[%d]: interrupted\n", tdata->id);
+		goto out;
+	}
+
+	for (i = 0; i < tdata->entries; i++) {
+		tdata->objs[i].value.id = i;
+		tdata->objs[i].value.tid = tdata->id;
+		err = insert_retry(&ht, &tdata->objs[i], test_rht_params);
+		if (err > 0) {
+			insert_retries += err;
+		} else if (err) {
+			pr_err("  thread[%d]: rhashtable_insert_fast failed\n",
+			       tdata->id);
+			goto out;
+		}
+	}
+	if (insert_retries)
+		pr_info("  thread[%d]: %u insertions retried due to memory pressure\n",
+			tdata->id, insert_retries);
+
+	err = thread_lookup_test(tdata);
+	if (err) {
+		pr_err("  thread[%d]: rhashtable_lookup_test failed\n",
+		       tdata->id);
+		goto out;
+	}
+
+	for (step = 10; step > 0; step--) {
+		for (i = 0; i < tdata->entries; i += step) {
+			if (tdata->objs[i].value.id == TEST_INSERT_FAIL)
+				continue;
+			err = rhashtable_remove_fast(&ht, &tdata->objs[i].node,
+			                             test_rht_params);
+			if (err) {
+				pr_err("  thread[%d]: rhashtable_remove_fast failed\n",
+				       tdata->id);
+				goto out;
+			}
+			tdata->objs[i].value.id = TEST_INSERT_FAIL;
+
+			cond_resched();
+		}
+		err = thread_lookup_test(tdata);
+		if (err) {
+			pr_err("  thread[%d]: rhashtable_lookup_test (2) failed\n",
+			       tdata->id);
+			goto out;
+		}
+	}
+out:
+	while (!kthread_should_stop()) {
+		set_current_state(TASK_INTERRUPTIBLE);
+		schedule();
+	}
+	return err;
+}
+
+static int __init test_rhashtable_next_key(void)
+{
+	struct rhashtable_params params = test_rht_params;
+	struct test_obj_val key_missing = { .id = 99999, .tid = 0 };
+	struct test_obj_val *prev_key = NULL;
+	struct rhashtable ht;
+	struct test_obj *objs, *cur;
+	int i, count = 0, err;
+	int visited_keys[8] = { 0 };
+	const int n = ARRAY_SIZE(visited_keys);
+
+	params.nelem_hint = n;
+
+	err = rhashtable_init(&ht, &params);
+	if (err)
+		return err;
+
+	objs = kzalloc_objs(*objs, n);
+	if (!objs) {
+		rhashtable_destroy(&ht);
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < n; i++) {
+		objs[i].value.id = i;
+		err = rhashtable_insert_fast(&ht, &objs[i].node, params);
+		if (err)
+			goto out;
+	}
+
+	rcu_read_lock();
+
+	/* NULL prev_key: walk from the beginning, expect all n elements. */
+	while ((cur = rhashtable_next_key(&ht, prev_key))) {
+		if (IS_ERR(cur)) {
+			err = -EINVAL;
+			goto unlock;
+		}
+		count++;
+		prev_key = &cur->value;
+		visited_keys[cur->value.id] = 1;
+		if (count > n)
+			break;
+	}
+
+	if (count != n) {
+		err = -EINVAL;
+		goto unlock;
+	}
+
+	for (i = 0; i < n; i++) {
+		if (!visited_keys[i]) {
+			err = -EINVAL;
+			goto unlock;
+		}
+	}
+
+	/* Non-existing prev_key: must return ERR_PTR(-ENOENT). */
+	cur = rhashtable_next_key(&ht, &key_missing);
+	if (!IS_ERR(cur) || PTR_ERR(cur) != -ENOENT)
+		err = -EINVAL;
+
+unlock:
+	rcu_read_unlock();
+out:
+	for (i = 0; i < n; i++)
+		rhashtable_remove_fast(&ht, &objs[i].node, params);
+	kfree(objs);
+	rhashtable_destroy(&ht);
+	return err;
+}
+
+static int __init test_rht_init(void)
+{
+	unsigned int entries;
+	int i, err, started_threads = 0, failed_threads = 0;
+	u64 total_time = 0;
+	struct thread_data *tdata;
+	struct test_obj *objs;
+
+	if (parm_entries < 0)
+		parm_entries = 1;
+
+	entries = min(parm_entries, MAX_ENTRIES);
+
+	test_rht_params.automatic_shrinking = shrinking;
+	test_rht_params.max_size = max_size ? : roundup_pow_of_two(entries);
+	test_rht_params.nelem_hint = size;
+
+	objs = vzalloc(array_size(sizeof(struct test_obj),
+				  test_rht_params.max_size + 1));
+	if (!objs)
+		return -ENOMEM;
+
+	pr_info("Running rhashtable test nelem=%d, max_size=%d, shrinking=%d\n",
+		size, max_size, shrinking);
+
+	for (i = 0; i < runs; i++) {
+		s64 time;
+
+		pr_info("Test %02d:\n", i);
+		memset(objs, 0, test_rht_params.max_size * sizeof(struct test_obj));
+
+		err = rhashtable_init(&ht, &test_rht_params);
+		if (err < 0) {
+			pr_warn("Test failed: Unable to initialize hashtable: %d\n",
+				err);
+			continue;
+		}
+
+		time = test_rhashtable(&ht, objs, entries);
+		rhashtable_destroy(&ht);
+		if (time < 0) {
+			vfree(objs);
+			pr_warn("Test failed: return code %lld\n", time);
+			return -EINVAL;
+		}
+
+		total_time += time;
+	}
+
+	pr_info("test if its possible to exceed max_size %d: %s\n",
+			test_rht_params.max_size, test_rhashtable_max(objs, entries) == 0 ?
+			"no, ok" : "YES, failed");
+	vfree(objs);
+
+	do_div(total_time, runs);
+	pr_info("Average test time: %llu\n", total_time);
+
+	test_insert_duplicates_run();
+
+	pr_info("Testing rhashtable_next_key: %s\n",
+		test_rhashtable_next_key() == 0 ? "pass" : "FAIL");
+
+	if (!tcount)
+		return 0;
+
+	pr_info("Testing concurrent rhashtable access from %d threads\n",
+	        tcount);
+	atomic_set(&startup_count, tcount);
+	tdata = vzalloc(array_size(tcount, sizeof(struct thread_data)));
+	if (!tdata)
+		return -ENOMEM;
+	objs  = vzalloc(array3_size(sizeof(struct test_obj), tcount, entries));
+	if (!objs) {
+		vfree(tdata);
+		return -ENOMEM;
+	}
+
+	test_rht_params.max_size = max_size ? :
+	                           roundup_pow_of_two(tcount * entries);
+	err = rhashtable_init(&ht, &test_rht_params);
+	if (err < 0) {
+		pr_warn("Test failed: Unable to initialize hashtable: %d\n",
+			err);
+		vfree(tdata);
+		vfree(objs);
+		return -EINVAL;
+	}
+	for (i = 0; i < tcount; i++) {
+		tdata[i].id = i;
+		tdata[i].entries = entries;
+		tdata[i].objs = objs + i * entries;
+		tdata[i].task = kthread_run(threadfunc, &tdata[i],
+		                            "rhashtable_thrad[%d]", i);
+		if (IS_ERR(tdata[i].task)) {
+			pr_err(" kthread_run failed for thread %d\n", i);
+			atomic_dec(&startup_count);
+		} else {
+			started_threads++;
+		}
+	}
+	if (wait_event_interruptible(startup_wait, atomic_read(&startup_count) == 0))
+		pr_err("  wait_event interruptible failed\n");
+	/* count is 0 now, set it to -1 and wake up all threads together */
+	atomic_dec(&startup_count);
+	wake_up_all(&startup_wait);
+	for (i = 0; i < tcount; i++) {
+		if (IS_ERR(tdata[i].task))
+			continue;
+		if ((err = kthread_stop(tdata[i].task))) {
+			pr_warn("Test failed: thread %d returned: %d\n",
+			        i, err);
+			failed_threads++;
+		}
+	}
+	rhashtable_destroy(&ht);
+	vfree(tdata);
+	vfree(objs);
+
+	/*
+	 * rhltable_remove is very expensive, default values can cause test
+	 * to run for 2 minutes or more,  use a smaller number instead.
+	 */
+	err = test_rhltable(entries / 16);
+	pr_info("Started %d threads, %d failed, rhltable test returns %d\n",
+	        started_threads, failed_threads, err);
+	return 0;
+}
+
+static void __exit test_rht_exit(void)
+{
+}
+
+module_init(test_rht_init);
+module_exit(test_rht_exit);
+
+MODULE_DESCRIPTION("Resizable, Scalable, Concurrent Hash Table test module");
+MODULE_LICENSE("GPL v2");