Re: [PATCH v2 12/20] KVM: selftests: Add APIs to override memory region types with custom memslots
From: Claudio Imbrenda
Date: Thu Sep 10 2026 - 06:36:07 EST
On Wed, 2 Sep 2026 09:41:15 -0700
Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
> 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.
>
> Tested-by: Itaru Kitayama <itaru.kitayama@xxxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Acked-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
> ---
> .../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 304ef6af3268..c8faa8a02b93 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)