Implement random number generator for guest code to randomize parts
of the test, making it less predictable and a more accurate reflection
of reality.
The random number generator chosen is the Park-Miller Linear
Congruential Generator, a fancy name for a basic and well-understood
random number generator entirely sufficient for this purpose. Each
vCPU calculates its own seed by adding its index to the seed provided.
Signed-off-by: Colton Lewis <coltonlewis@xxxxxxxxxx>
---
tools/testing/selftests/kvm/include/test_util.h | 7 +++++++
tools/testing/selftests/kvm/lib/test_util.c | 17 +++++++++++++++++
2 files changed, 24 insertions(+)
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index befc754ce9b3..9e4f36a1a8b0 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -152,4 +152,11 @@ static inline void *align_ptr_up(void *x, size_t size)
return (void *)align_up((unsigned long)x, size);
}
+struct guest_random_state {
+ uint32_t seed;
+};
+
+struct guest_random_state new_guest_random_state(uint32_t seed);
+uint32_t guest_random_u32(struct guest_random_state *state);
+
#endif /* SELFTEST_KVM_TEST_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
index 6d23878bbfe1..c4d2749fb2c3 100644
--- a/tools/testing/selftests/kvm/lib/test_util.c
+++ b/tools/testing/selftests/kvm/lib/test_util.c
@@ -17,6 +17,23 @@
#include "test_util.h"
+/*
+ * Random number generator that is usable from guest code. This is the
+ * Park-Miller LCG using standard constants.
+ */
+
+struct guest_random_state new_guest_random_state(uint32_t seed)
+{
+ struct guest_random_state s = {.seed = seed};
+ return s;
+}
+
+uint32_t guest_random_u32(struct guest_random_state *state)
+{
+ state->seed = (uint64_t)state->seed * 48271 % ((uint32_t)(1 << 31) - 1);
+ return state->seed;
+}
+
/*
* Parses "[0-9]+[kmgt]?".
*/
--
2.38.1.273.g43a17bfeac-goog
