KVM: selftests: Read per-page value into local var when verifying dirty_log_test

Cache the page's value during verification in a local variable, re-reading
from the pointer is ugly and error prone, e.g. allows for bugs like
checking the pointer itself instead of the value.

No functional change intended.

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/r/20250111003004.1235645-7-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index 08cbecd1a135e4118a4c450da8c974f0760c9796..5a04a7bd73e0d432a0d74dc475d047555a892d68 100644 (file)
--- a/tools/testing/selftests/kvm/dirty_log_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_test.c
@@ -520,11 +520,10 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
 {
        uint64_t page, nr_dirty_pages = 0, nr_clean_pages = 0;
        uint64_t step = vm_num_host_pages(mode, 1);
-       uint64_t *value_ptr;
        uint64_t min_iter = 0;
 
        for (page = 0; page < host_num_pages; page += step) {
-               value_ptr = host_test_mem + page * host_page_size;
+               uint64_t val = *(uint64_t *)(host_test_mem + page * host_page_size);
 
                /* If this is a special page that we were tracking... */
                if (__test_and_clear_bit_le(page, host_bmap_track)) {
@@ -545,11 +544,10 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
                         * the corresponding page should be either the
                         * previous iteration number or the current one.
                         */
-                       matched = (*value_ptr == iteration ||
-                                  *value_ptr == iteration - 1);
+                       matched = (val == iteration || val == iteration - 1);
 
                        if (host_log_mode == LOG_MODE_DIRTY_RING && !matched) {
-                               if (*value_ptr == iteration - 2 && min_iter <= iteration - 2) {
+                               if (val == iteration - 2 && min_iter <= iteration - 2) {
                                        /*
                                         * Short answer: this case is special
                                         * only for dirty ring test where the
@@ -597,7 +595,7 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
                        TEST_ASSERT(matched,
                                    "Set page %"PRIu64" value %"PRIu64
                                    " incorrect (iteration=%"PRIu64")",
-                                   page, *value_ptr, iteration);
+                                   page, val, iteration);
                } else {
                        nr_clean_pages++;
                        /*
@@ -619,11 +617,11 @@ static void vm_dirty_log_verify(enum vm_guest_mode mode, unsigned long *bmap)
                         *     we'll see that page P is cleared, with
                         *     value "iteration-1".
                         */
-                       TEST_ASSERT(*value_ptr <= iteration,
+                       TEST_ASSERT(val <= iteration,
                                    "Clear page %"PRIu64" value %"PRIu64
                                    " incorrect (iteration=%"PRIu64")",
-                                   page, *value_ptr, iteration);
-                       if (*value_ptr == iteration) {
+                                   page, val, iteration);
+                       if (val == iteration) {
                                /*
                                 * This page is _just_ modified; it
                                 * should report its dirtyness in the