KVM: selftests: Setup vcpu_alias only for minor mode test

This fixes two things:

- Unbreaks MISSING mode test on anonymous memory type

- Prefault alias mem before uffd thread creations, otherwise the uffd
  thread timing will be inaccurate when guest mem size is large, because
  it'll take prefault time into total time.

Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: James Houghton <jthoughton@google.com>
Link: https://lore.kernel.org/r/20230427201112.2164776-2-peterx@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/demand_paging_test.c b/tools/testing/selftests/kvm/demand_paging_test.c
index 2439c40..9c18686 100644 (file)
--- a/tools/testing/selftests/kvm/demand_paging_test.c
+++ b/tools/testing/selftests/kvm/demand_paging_test.c
@@ -128,6 +128,7 @@ static void prefault_mem(void *alias, uint64_t len)
 
 static void run_test(enum vm_guest_mode mode, void *arg)
 {
+       struct memstress_vcpu_args *vcpu_args;
        struct test_params *p = arg;
        struct uffd_desc **uffd_descs = NULL;
        struct timespec start;
@@ -145,24 +146,24 @@ static void run_test(enum vm_guest_mode mode, void *arg)
                    "Failed to allocate buffer for guest data pattern");
        memset(guest_data_prototype, 0xAB, demand_paging_size);
 
+       if (p->uffd_mode == UFFDIO_REGISTER_MODE_MINOR) {
+               for (i = 0; i < nr_vcpus; i++) {
+                       vcpu_args = &memstress_args.vcpu_args[i];
+                       prefault_mem(addr_gpa2alias(vm, vcpu_args->gpa),
+                                    vcpu_args->pages * memstress_args.guest_page_size);
+               }
+       }
+
        if (p->uffd_mode) {
                uffd_descs = malloc(nr_vcpus * sizeof(struct uffd_desc *));
                TEST_ASSERT(uffd_descs, "Memory allocation failed");
-
                for (i = 0; i < nr_vcpus; i++) {
-                       struct memstress_vcpu_args *vcpu_args;
                        void *vcpu_hva;
-                       void *vcpu_alias;
 
                        vcpu_args = &memstress_args.vcpu_args[i];
 
                        /* Cache the host addresses of the region */
                        vcpu_hva = addr_gpa2hva(vm, vcpu_args->gpa);
-                       vcpu_alias = addr_gpa2alias(vm, vcpu_args->gpa);
-
-                       prefault_mem(vcpu_alias,
-                               vcpu_args->pages * memstress_args.guest_page_size);
-
                        /*
                         * Set up user fault fd to handle demand paging
                         * requests.