[PATCH 12/20] KVM: selftests: Add APIs to override memory region types with custom memslots
From: Sean Christopherson
Date: Wed Aug 26 2026 - 19:08:33 EST
Add and use APIs to override memory region types instead of open coding the
logic in tests, partly to dedup test code, but mostly to add some amount of
protection against conflicting overrides. This will allow converting more
tests to override memory regions without taking on too much risk of bugs in
the long term, e.g. due to silently overriding a region multiple times.
Deliberately "unroll" the loops in __vm_create() and the CMMA test's
create_main_memslot() to avoid filling all memslots in anticipation of
adding an "extra" memslot that is for test use and *only* test use, i.e.
shouldn't be configured by core library code.
Converting tests to overriding memory regions will allow taking the region
type instead of the raw memslot in the physical page allocator APIs.
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
.../selftests/kvm/arm64/page_fault_test.c | 18 +++++------
.../testing/selftests/kvm/include/kvm_util.h | 30 +++++++++++++++++++
tools/testing/selftests/kvm/lib/kvm_util.c | 8 +++--
tools/testing/selftests/kvm/s390/cmma_test.c | 19 ++++--------
4 files changed, 49 insertions(+), 26 deletions(-)
diff --git a/tools/testing/selftests/kvm/arm64/page_fault_test.c b/tools/testing/selftests/kvm/arm64/page_fault_test.c
index 6bb3d82906b2..b0e3fc8cd76a 100644
--- a/tools/testing/selftests/kvm/arm64/page_fault_test.c
+++ b/tools/testing/selftests/kvm/arm64/page_fault_test.c
@@ -597,18 +597,16 @@ static void setup_memslots(struct kvm_vm *vm, struct test_params *p)
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0,
CODE_AND_DATA_MEMSLOT, code_npages, 0);
- vm->memslots[MEM_REGION_CODE] = CODE_AND_DATA_MEMSLOT;
- vm->memslots[MEM_REGION_DATA] = CODE_AND_DATA_MEMSLOT;
+ ____vm_override_mem_region(vm, MEM_REGION_CODE, CODE_AND_DATA_MEMSLOT);
+ ____vm_override_mem_region(vm, MEM_REGION_DATA, CODE_AND_DATA_MEMSLOT);
- vm_userspace_mem_region_add(vm, p->src_type, data_gpa - pt_size,
- PAGE_TABLE_MEMSLOT, pt_size / guest_page_size,
- p->test_desc->pt_memslot_flags);
- vm->memslots[MEM_REGION_PT] = PAGE_TABLE_MEMSLOT;
+ __vm_override_mem_region(vm, MEM_REGION_PT, p->src_type, data_gpa - pt_size,
+ PAGE_TABLE_MEMSLOT, pt_size / guest_page_size,
+ p->test_desc->pt_memslot_flags);
- vm_userspace_mem_region_add(vm, p->src_type, data_gpa, TEST_DATA_MEMSLOT,
- data_size / guest_page_size,
- p->test_desc->data_memslot_flags);
- vm->memslots[MEM_REGION_TEST_DATA] = TEST_DATA_MEMSLOT;
+ __vm_override_mem_region(vm, MEM_REGION_TEST_DATA, p->src_type, data_gpa,
+ TEST_DATA_MEMSLOT, data_size / guest_page_size,
+ p->test_desc->data_memslot_flags);
}
static void setup_ucall(struct kvm_vm *vm)
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 70e77992dd2f..14f87c8a00ec 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -704,6 +704,36 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
gpa_t gpa, u32 slot, u64 npages, u32 flags,
int guest_memfd_fd, u64 guest_memfd_offset);
+
+static inline void ____vm_override_mem_region(struct kvm_vm *vm,
+ enum kvm_mem_region_type type,
+ u32 slot)
+{
+ TEST_ASSERT(vm->memslots[type] == KVM_INVALID_MEMSLOT,
+ "Memory region type '%u' was already overridden with slot=%u",
+ type, vm->memslots[type]);
+
+ vm->memslots[type] = slot;
+}
+
+static inline void __vm_override_mem_region(struct kvm_vm *vm,
+ enum kvm_mem_region_type type,
+ enum vm_mem_backing_src_type src_type,
+ gpa_t gpa, u32 slot, u64 npages,
+ u32 flags)
+{
+ ____vm_override_mem_region(vm, type, slot);
+ vm_userspace_mem_region_add(vm, src_type, gpa, slot, npages, flags);
+}
+
+static inline void vm_override_mem_region(struct kvm_vm *vm,
+ enum kvm_mem_region_type type,
+ enum vm_mem_backing_src_type src_type,
+ gpa_t gpa, u32 slot, u64 npages)
+{
+ __vm_override_mem_region(vm, type, src_type, gpa, slot, npages, 0);
+}
+
#ifndef vm_arch_has_protected_memory
static inline bool vm_arch_has_protected_memory(struct kvm_vm *vm)
{
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 56df5b1d9c79..781af2928d04 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -495,7 +495,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus,
nr_extra_pages);
struct userspace_mem_region *slot0;
struct kvm_vm *vm;
- int i, flags;
+ int flags;
kvm_set_files_rlimit(nr_runnable_vcpus);
@@ -513,8 +513,10 @@ struct kvm_vm *__vm_create(struct vm_shape shape, u32 nr_runnable_vcpus,
flags |= KVM_MEM_GUEST_MEMFD;
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, nr_pages, flags);
- for (i = 0; i < NR_MEM_REGIONS; i++)
- vm->memslots[i] = 0;
+ ____vm_override_mem_region(vm, MEM_REGION_CODE, 0);
+ ____vm_override_mem_region(vm, MEM_REGION_PT, 0);
+ ____vm_override_mem_region(vm, MEM_REGION_DATA, 0);
+ ____vm_override_mem_region(vm, MEM_REGION_TEST_DATA, 0);
kvm_vm_elf_load(vm, program_invocation_name);
diff --git a/tools/testing/selftests/kvm/s390/cmma_test.c b/tools/testing/selftests/kvm/s390/cmma_test.c
index 15d81b2ed7ad..73387cc3bca7 100644
--- a/tools/testing/selftests/kvm/s390/cmma_test.c
+++ b/tools/testing/selftests/kvm/s390/cmma_test.c
@@ -102,24 +102,17 @@ static void guest_dirty_test_data(void)
static void create_main_memslot(struct kvm_vm *vm)
{
- int i;
-
vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, 0, 0, MAIN_PAGE_COUNT, 0);
- /* set the array of memslots to zero like __vm_create does */
- for (i = 0; i < NR_MEM_REGIONS; i++)
- vm->memslots[i] = 0;
+ ____vm_override_mem_region(vm, MEM_REGION_CODE, 0);
+ ____vm_override_mem_region(vm, MEM_REGION_PT, 0);
+ ____vm_override_mem_region(vm, MEM_REGION_DATA, 0);
}
static void create_test_memslot(struct kvm_vm *vm)
{
- vm_userspace_mem_region_add(vm,
- VM_MEM_SRC_ANONYMOUS,
- TEST_DATA_START_GFN << vm->page_shift,
- TEST_DATA_MEMSLOT,
- TEST_DATA_PAGE_COUNT,
- 0
- );
- vm->memslots[MEM_REGION_TEST_DATA] = TEST_DATA_MEMSLOT;
+ vm_override_mem_region(vm, MEM_REGION_TEST_DATA, VM_MEM_SRC_ANONYMOUS,
+ TEST_DATA_START_GFN << vm->page_shift,
+ TEST_DATA_MEMSLOT, TEST_DATA_PAGE_COUNT);
}
static void create_memslots(struct kvm_vm *vm)
--
2.55.0.887.g758fc8c411-goog