KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()

vm_get_max_gfn() casts vm->max_gfn from a uint64_t to an unsigned int,
which causes the upper 32-bits of the max_gfn to get truncated.

Nobody noticed until now likely because vm_get_max_gfn() is only used
as a mechanism to create a memslot in an unused region of the guest
physical address space (the top), and the top of the 32-bit physical
address space was always good enough.

This fix reveals a bug in memslot_modification_stress_test which was
trying to create a dummy memslot past the end of guest physical memory.
Fix that by moving the dummy memslot lower.

Fixes: 52200d0d944e ("KVM: selftests: Remove duplicate guest mode handling")
Reviewed-by: Venkatesh Srinivas <venkateshs@chromium.org>
Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210521173828.1180619-1-dmatlack@google.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index a8f022794ce3cbf5640aae6aed274196d540cb1d..2e0d253dabd644adb893b4802955cb96c376c3b8 100644 (file)
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -302,7 +302,7 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm);
 
 unsigned int vm_get_page_size(struct kvm_vm *vm);
 unsigned int vm_get_page_shift(struct kvm_vm *vm);
-unsigned int vm_get_max_gfn(struct kvm_vm *vm);
+uint64_t vm_get_max_gfn(struct kvm_vm *vm);
 int vm_get_fd(struct kvm_vm *vm);
 
 unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size);

diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1255744758e360003bc3414436aa049f7f0f992d..ea3f0db85b3e7ffbe2de51d780b19a96dbabecd0 100644 (file)
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -2117,7 +2117,7 @@ unsigned int vm_get_page_shift(struct kvm_vm *vm)
        return vm->page_shift;
 }
 
-unsigned int vm_get_max_gfn(struct kvm_vm *vm)
+uint64_t vm_get_max_gfn(struct kvm_vm *vm)
 {
        return vm->max_gfn;
 }

diff --git a/tools/testing/selftests/kvm/lib/perf_test_util.c b/tools/testing/selftests/kvm/lib/perf_test_util.c
index 81490b9b4e32a96ecdadf918a6136fcd83aa5b9e..abf381800a5909726f5391feeece8bbea352c518 100644 (file)
--- a/tools/testing/selftests/kvm/lib/perf_test_util.c
+++ b/tools/testing/selftests/kvm/lib/perf_test_util.c
@@ -2,6 +2,7 @@
 /*
  * Copyright (C) 2020, Google LLC.
  */
+#include <inttypes.h>
 
 #include "kvm_util.h"
 #include "perf_test_util.h"
@@ -80,7 +81,8 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus,
         */
        TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
                    "Requested more guest memory than address space allows.\n"
-                   "    guest pages: %lx max gfn: %x vcpus: %d wss: %lx]\n",
+                   "    guest pages: %" PRIx64 " max gfn: %" PRIx64
+                   " vcpus: %d wss: %" PRIx64 "]\n",
                    guest_num_pages, vm_get_max_gfn(vm), vcpus,
                    vcpu_memory_bytes);
 

diff --git a/tools/testing/selftests/kvm/memslot_modification_stress_test.c b/tools/testing/selftests/kvm/memslot_modification_stress_test.c
index 6096bf0a5b34f0f8cb37cc15310e76fc721c73a1..98351ba0933cdb4e89281cdaf98c5a8ccc85a05f 100644 (file)
--- a/tools/testing/selftests/kvm/memslot_modification_stress_test.c
+++ b/tools/testing/selftests/kvm/memslot_modification_stress_test.c
@@ -71,14 +71,22 @@ struct memslot_antagonist_args {
 };
 
 static void add_remove_memslot(struct kvm_vm *vm, useconds_t delay,
-                             uint64_t nr_modifications, uint64_t gpa)
+                              uint64_t nr_modifications)
 {
+       const uint64_t pages = 1;
+       uint64_t gpa;
        int i;
 
+       /*
+        * Add the dummy memslot just below the perf_test_util memslot, which is
+        * at the top of the guest physical address space.
+        */
+       gpa = guest_test_phys_mem - pages * vm_get_page_size(vm);
+
        for (i = 0; i < nr_modifications; i++) {
                usleep(delay);
                vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, gpa,
-                                           DUMMY_MEMSLOT_INDEX, 1, 0);
+                                           DUMMY_MEMSLOT_INDEX, pages, 0);
 
                vm_mem_region_delete(vm, DUMMY_MEMSLOT_INDEX);
        }
@@ -120,11 +128,7 @@ static void run_test(enum vm_guest_mode mode, void *arg)
        pr_info("Started all vCPUs\n");
 
        add_remove_memslot(vm, p->memslot_modification_delay,
-                          p->nr_memslot_modifications,
-                          guest_test_phys_mem +
-                          (guest_percpu_mem_size * nr_vcpus) +
-                          perf_test_args.host_page_size +
-                          perf_test_args.guest_page_size);
+                          p->nr_memslot_modifications);
 
        run_vcpus = false;