[PATCH v4 05/19] KVM: selftests: Add helper to generate random u64 in range [min,max]

[Josh Hilke <jrhilke@google.com>]

Introduce kvm_random_u64_in_range(state, min, max). This function
returns a random u64 in the inclusive range of [min, max] using a struct
kvm_random_state.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Josh Hilke <jrhilke@google.com>
---
 .../testing/selftests/kvm/include/test_util.h  |  3 +++
 tools/testing/selftests/kvm/lib/test_util.c    | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index ae39c4293b9a..d601227dbdba 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -132,6 +132,9 @@ static inline uint64_t kvm_random_u64(struct kvm_random_state *state)
 	return ((uint64_t)kvm_random_u32(state) << 32) | kvm_random_u32(state);
 }
 
+uint64_t kvm_random_u64_in_range(struct kvm_random_state *state, uint64_t min,
+				 uint64_t max);
+
 enum vm_mem_backing_src_type {
 	VM_MEM_SRC_ANONYMOUS,
 	VM_MEM_SRC_ANONYMOUS_THP,
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index e342d9fb4771..dc47ed9736e9 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -42,6 +42,24 @@ uint32_t kvm_random_u32(struct kvm_random_state *state)
 	return state->seed;
 }
 
+/* Returns a random u64 in the inclusive range [min, max] */
+uint64_t kvm_random_u64_in_range(struct kvm_random_state *state, uint64_t min,
+				 uint64_t max)
+{
+	uint64_t value;
+	uint64_t range;
+
+	TEST_ASSERT(min <= max, "PEBKAC, min = 0x%lx, max = 0x%lx", min, max);
+
+	value = kvm_random_u64(state);
+
+	range = max - min;
+	if (range == ULLONG_MAX)
+		return value;
+
+	return min + (value % (range + 1));
+}
+
 /*
  * Parses "[0-9]+[kmgt]?".
  */
-- 
2.54.0.929.g9b7fa37559-goog