[PATCH v4 12/16] KVM: selftests: Add a read-only mprotect() phase to mmu_stress_test

Sean Christopherson
2024-11-28T00:56:11Z

Add a third phase of mmu_stress_test to verify that mprotect()ing guest
memory to make it read-only doesn't cause explosions, e.g. to verify KVM
correctly handles the resulting mmu_notifier invalidations.

Reviewed-by: James Houghton <jthoughton@google.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/mmu_stress_test.c | 22 +++++++++++++++----
1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/kvm/mmu_stress_test.c b/tools/testing/selftests/kvm/mmu_stress_test.c
index c6bf18cb7c89..0918fade9267 100644
--- a/tools/testing/selftests/kvm/mmu_stress_test.c
+++ b/tools/testing/selftests/kvm/mmu_stress_test.c
@@ -28,6 +28,10 @@ static void guest_code(uint64_t start_gpa, uint64_t end_gpa, uint64_t stride)
GUEST_SYNC(i);
}

+ for (gpa = start_gpa; gpa < end_gpa; gpa += stride)
+ *((volatile uint64_t *)gpa);
+ GUEST_SYNC(2);
+
GUEST_ASSERT(0);
}

@@ -95,6 +99,10 @@ static void *vcpu_worker(void *data)
run_vcpu(vcpu, 1);
rendezvous_with_boss();

+ /* Stage 2, read all of guest memory, which is now read-only. */
+ run_vcpu(vcpu, 2);
+ rendezvous_with_boss();
+
return NULL;
}

@@ -175,7 +183,7 @@ int main(int argc, char *argv[])
const uint64_t start_gpa = SZ_4G;
const int first_slot = 1;

- struct timespec time_start, time_run1, time_reset, time_run2;
+ struct timespec time_start, time_run1, time_reset, time_run2, time_ro;
uint64_t max_gpa, gpa, slot_size, max_mem, i;
int max_slots, slot, opt, fd;
bool hugepages = false;
@@ -279,14 +287,20 @@ int main(int argc, char *argv[])
rendezvous_with_vcpus(&time_reset, "reset");
rendezvous_with_vcpus(&time_run2, "run 2");

+ mprotect(mem, slot_size, PROT_READ);
+ rendezvous_with_vcpus(&time_ro, "mprotect RO");
+
+ time_ro = timespec_sub(time_ro, time_run2);
time_run2 = timespec_sub(time_run2, time_reset);
- time_reset = timespec_sub(time_reset, time_run1);
+ time_reset = timespec_sub(time_reset, time_run1);
time_run1 = timespec_sub(time_run1, time_start);

- pr_info("run1 = %ld.%.9lds, reset = %ld.%.9lds, run2 = %ld.%.9lds\n",
+ pr_info("run1 = %ld.%.9lds, reset = %ld.%.9lds, run2 = %ld.%.9lds, "
+ "ro = %ld.%.9lds\n",
time_run1.tv_sec, time_run1.tv_nsec,
time_reset.tv_sec, time_reset.tv_nsec,
- time_run2.tv_sec, time_run2.tv_nsec);
+ time_run2.tv_sec, time_run2.tv_nsec,
+ time_ro.tv_sec, time_ro.tv_nsec);

/*
* Delete even numbered slots (arbitrary) and unmap the first half of
--
2.47.0.338.g60cca15819-goog