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

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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>
This commit is contained in:
David Matlack 2021-05-21 17:38:28 +00:00 committed by Paolo Bonzini
parent cad347fab1
commit ef4c9f4f65
4 changed files with 16 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
tools/testing/selftests/kvm/include/kvm_util.h
View File

@ -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_size(struct kvm_vm *vm);
unsigned int vm_get_page_shift(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); int vm_get_fd(struct kvm_vm *vm);
unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size); unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size);

2
tools/testing/selftests/kvm/lib/kvm_util.c
View File

@ -2117,7 +2117,7 @@ unsigned int vm_get_page_shift(struct kvm_vm *vm)
return vm->page_shift; 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; return vm->max_gfn;
} }

4
tools/testing/selftests/kvm/lib/perf_test_util.c
View File

@ -2,6 +2,7 @@
/* /*
* Copyright (C) 2020, Google LLC. * Copyright (C) 2020, Google LLC.
*/ */
#include <inttypes.h>
#include "kvm_util.h" #include "kvm_util.h"
#include "perf_test_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), TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),
"Requested more guest memory than address space allows.\n" "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, guest_num_pages, vm_get_max_gfn(vm), vcpus,
vcpu_memory_bytes); vcpu_memory_bytes);

18
tools/testing/selftests/kvm/memslot_modification_stress_test.c
View File

@ -71,14 +71,22 @@ struct memslot_antagonist_args {
}; };
static void add_remove_memslot(struct kvm_vm *vm, useconds_t delay, 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; 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++) { for (i = 0; i < nr_modifications; i++) {
usleep(delay); usleep(delay);
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, gpa, 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); 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"); pr_info("Started all vCPUs\n");
add_remove_memslot(vm, p->memslot_modification_delay, add_remove_memslot(vm, p->memslot_modification_delay,
p->nr_memslot_modifications, 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);
run_vcpus = false; run_vcpus = false;