KVM: selftests: Create a separate dirty bitmap per slot

The calculation to get the per-slot dirty bitmap was incorrect leading
to a buffer overrun. Fix it by splitting out the dirty bitmap into a
separate bitmap per slot.

Fixes: 609e6202ea5f ("KVM: selftests: Support multiple slots in dirty_log_perf_test")
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Message-Id: <20210917173657.44011-4-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/dirty_log_perf_test.c b/tools/testing/selftests/kvm/dirty_log_perf_test.c
index b076dfa3ae1bfdf76ea0d828e549699b41404321..7ffab5bd5ce55a59da6e128e226847cf0c765353 100644 (file)
--- a/tools/testing/selftests/kvm/dirty_log_perf_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_perf_test.c
@@ -118,42 +118,64 @@ static inline void disable_dirty_logging(struct kvm_vm *vm, int slots)
        toggle_dirty_logging(vm, slots, false);
 }
 
-static void get_dirty_log(struct kvm_vm *vm, int slots, unsigned long *bitmap,
-                         uint64_t nr_pages)
+static void get_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[], int slots)
 {
-       uint64_t slot_pages = nr_pages / slots;
        int i;
 
        for (i = 0; i < slots; i++) {
                int slot = PERF_TEST_MEM_SLOT_INDEX + i;
-               unsigned long *slot_bitmap = bitmap + i * slot_pages;
 
-               kvm_vm_get_dirty_log(vm, slot, slot_bitmap);
+               kvm_vm_get_dirty_log(vm, slot, bitmaps[i]);
        }
 }
 
-static void clear_dirty_log(struct kvm_vm *vm, int slots, unsigned long *bitmap,
-                           uint64_t nr_pages)
+static void clear_dirty_log(struct kvm_vm *vm, unsigned long *bitmaps[],
+                           int slots, uint64_t pages_per_slot)
 {
-       uint64_t slot_pages = nr_pages / slots;
        int i;
 
        for (i = 0; i < slots; i++) {
                int slot = PERF_TEST_MEM_SLOT_INDEX + i;
-               unsigned long *slot_bitmap = bitmap + i * slot_pages;
 
-               kvm_vm_clear_dirty_log(vm, slot, slot_bitmap, 0, slot_pages);
+               kvm_vm_clear_dirty_log(vm, slot, bitmaps[i], 0, pages_per_slot);
        }
 }
 
+static unsigned long **alloc_bitmaps(int slots, uint64_t pages_per_slot)
+{
+       unsigned long **bitmaps;
+       int i;
+
+       bitmaps = malloc(slots * sizeof(bitmaps[0]));
+       TEST_ASSERT(bitmaps, "Failed to allocate bitmaps array.");
+
+       for (i = 0; i < slots; i++) {
+               bitmaps[i] = bitmap_zalloc(pages_per_slot);
+               TEST_ASSERT(bitmaps[i], "Failed to allocate slot bitmap.");
+       }
+
+       return bitmaps;
+}
+
+static void free_bitmaps(unsigned long *bitmaps[], int slots)
+{
+       int i;
+
+       for (i = 0; i < slots; i++)
+               free(bitmaps[i]);
+
+       free(bitmaps);
+}
+
 static void run_test(enum vm_guest_mode mode, void *arg)
 {
        struct test_params *p = arg;
        pthread_t *vcpu_threads;
        struct kvm_vm *vm;
-       unsigned long *bmap;
+       unsigned long **bitmaps;
        uint64_t guest_num_pages;
        uint64_t host_num_pages;
+       uint64_t pages_per_slot;
        int vcpu_id;
        struct timespec start;
        struct timespec ts_diff;
@@ -171,7 +193,9 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        guest_num_pages = (nr_vcpus * guest_percpu_mem_size) >> vm_get_page_shift(vm);
        guest_num_pages = vm_adjust_num_guest_pages(mode, guest_num_pages);
        host_num_pages = vm_num_host_pages(mode, guest_num_pages);
-       bmap = bitmap_zalloc(host_num_pages);
+       pages_per_slot = host_num_pages / p->slots;
+
+       bitmaps = alloc_bitmaps(p->slots, pages_per_slot);
 
        if (dirty_log_manual_caps) {
                cap.cap = KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2;
@@ -239,7 +263,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
                        iteration, ts_diff.tv_sec, ts_diff.tv_nsec);
 
                clock_gettime(CLOCK_MONOTONIC, &start);
-               get_dirty_log(vm, p->slots, bmap, host_num_pages);
+               get_dirty_log(vm, bitmaps, p->slots);
                ts_diff = timespec_elapsed(start);
                get_dirty_log_total = timespec_add(get_dirty_log_total,
                                                   ts_diff);
@@ -248,7 +272,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
 
                if (dirty_log_manual_caps) {
                        clock_gettime(CLOCK_MONOTONIC, &start);
-                       clear_dirty_log(vm, p->slots, bmap, host_num_pages);
+                       clear_dirty_log(vm, bitmaps, p->slots, pages_per_slot);
                        ts_diff = timespec_elapsed(start);
                        clear_dirty_log_total = timespec_add(clear_dirty_log_total,
                                                             ts_diff);
@@ -281,7 +305,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
                        clear_dirty_log_total.tv_nsec, avg.tv_sec, avg.tv_nsec);
        }
 
-       free(bmap);
+       free_bitmaps(bitmaps, p->slots);
        free(vcpu_threads);
        perf_test_destroy_vm(vm);
 }