[PATCH 5.12 131/296] KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn()

Greg Kroah-Hartman
2021-05-31T16:31:45Z

From: David Matlack <dmatlack@google.com>

commit ef4c9f4f654622fa15b7a94a9bd1f19e76bb7feb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/testing/selftests/kvm/include/kvm_util.h | 2 -
tools/testing/selftests/kvm/lib/kvm_util.c | 2 -
tools/testing/selftests/kvm/lib/perf_test_util.c | 4 +-
tools/testing/selftests/kvm/memslot_modification_stress_test.c | 18 ++++++----
4 files changed, 16 insertions(+), 10 deletions(-)

--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -295,7 +295,7 @@ bool vm_is_unrestricted_guest(struct kvm

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);
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1969,7 +1969,7 @@ unsigned int vm_get_page_shift(struct kv
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;
}
--- 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
*/
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);

--- 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
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;