On Fri, 19 Jun 2026 at 01:32, Ackerley Tng via B4 Relay <[email protected]> wrote: > > From: Ackerley Tng <[email protected]> > > Update the private memory conversions selftest to also test conversions > that are done "in-place" via per-guest_memfd memory attributes. In-place > conversions require the host to be able to mmap() the guest_memfd so that > the host and guest can share the same backing physical memory. > > This includes several updates, that are conditioned on the system > supporting per-guest_memfd attributes (kvm_has_gmem_attributes): > > 1. Set up guest_memfd requesting MMAP and INIT_SHARED. > > 2. With in-place conversions, the host's mapping points directly to the > guest's memory. When the guest converts a region to private, host access > to that region is blocked. Update the test to expect a SIGBUS when > attempting to access the host virtual address (HVA) of private memory. > > 3. Use vm_mem_set_memory_attributes(), which chooses how to set memory > attributes based on whether kvm_has_gmem_attributes. > > Restrict the test to using VM_MEM_SRC_SHMEM because guest_memfd's required > mmap() flags and page sizes happens to align with those of > VM_MEM_SRC_SHMEM. As long as VM_MEM_SRC_SHMEM is used for src_type, > vm_mem_add() works as intended. > > Signed-off-by: Ackerley Tng <[email protected]> > Co-developed-by: Sean Christopherson <[email protected]> > Signed-off-by: Sean Christopherson <[email protected]>
Reviewed-by: Fuad Tabba <[email protected]> Cheers, /fuad > --- > .../kvm/x86/private_mem_conversions_test.c | 44 > ++++++++++++++++++---- > 1 file changed, 36 insertions(+), 8 deletions(-) > > diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c > b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c > index 289ad10063fca..4308c67952310 100644 > --- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c > +++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c > @@ -306,9 +306,12 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu) > if (do_fallocate) > vm_guest_mem_fallocate(vm, gpa, size, map_shared); > > - if (set_attributes) > - vm_set_memory_attributes(vm, gpa, size, > - map_shared ? 0 : > KVM_MEMORY_ATTRIBUTE_PRIVATE); > + if (set_attributes) { > + u64 attrs = map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE; > + > + vm_mem_set_memory_attributes(vm, gpa, size, attrs); > + } > + > run->hypercall.ret = 0; > } > > @@ -352,8 +355,20 @@ static void *__test_mem_conversions(void *__vcpu) > size_t nr_bytes = min_t(size_t, > vm->page_size, size - i); > u8 *hva = addr_gpa2hva(vm, gpa + i); > > - /* In all cases, the host should observe the > shared data. */ > - memcmp_h(hva, gpa + i, uc.args[3], nr_bytes); > + /* > + * When using per-guest_memfd memory > attributes, > + * i.e. in-place conversion, host accesses > will > + * point at guest memory and should SIGBUS > when > + * guest memory is private. When using per-VM > + * attributes, i.e. separate backing for > shared > + * vs. private, the host should always observe > + * the shared data. > + */ > + if (kvm_has_gmem_attributes && > + uc.args[0] == SYNC_PRIVATE) > + TEST_EXPECT_SIGBUS(READ_ONCE(*hva)); > + else > + memcmp_h(hva, gpa + i, uc.args[3], > nr_bytes); > > /* For shared, write the new pattern to guest > memory. */ > if (uc.args[0] == SYNC_SHARED) > @@ -382,6 +397,7 @@ static void test_mem_conversions(enum > vm_mem_backing_src_type src_type, u32 nr_v > const size_t slot_size = memfd_size / nr_memslots; > struct kvm_vcpu *vcpus[KVM_MAX_VCPUS]; > pthread_t threads[KVM_MAX_VCPUS]; > + u64 gmem_flags; > struct kvm_vm *vm; > int memfd, i; > > @@ -397,12 +413,17 @@ static void test_mem_conversions(enum > vm_mem_backing_src_type src_type, u32 nr_v > > vm_enable_cap(vm, KVM_CAP_EXIT_HYPERCALL, (1 << > KVM_HC_MAP_GPA_RANGE)); > > - memfd = vm_create_guest_memfd(vm, memfd_size, 0); > + if (kvm_has_gmem_attributes) > + gmem_flags = GUEST_MEMFD_FLAG_MMAP | > GUEST_MEMFD_FLAG_INIT_SHARED; > + else > + gmem_flags = 0; > + > + memfd = vm_create_guest_memfd(vm, memfd_size, gmem_flags); > > for (i = 0; i < nr_memslots; i++) > vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i, > BASE_DATA_SLOT + i, slot_size / vm->page_size, > - KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0); > + KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, > gmem_flags); > > for (i = 0; i < nr_vcpus; i++) { > gpa_t gpa = BASE_DATA_GPA + i * per_cpu_size; > @@ -452,17 +473,24 @@ static void usage(const char *cmd) > > int main(int argc, char *argv[]) > { > - enum vm_mem_backing_src_type src_type = DEFAULT_VM_MEM_SRC; > + enum vm_mem_backing_src_type src_type; > u32 nr_memslots = 1; > u32 nr_vcpus = 1; > int opt; > > TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & > BIT(KVM_X86_SW_PROTECTED_VM)); > > + src_type = kvm_has_gmem_attributes ? VM_MEM_SRC_SHMEM : > + DEFAULT_VM_MEM_SRC; > + > while ((opt = getopt(argc, argv, "hm:s:n:")) != -1) { > switch (opt) { > case 's': > src_type = parse_backing_src_type(optarg); > + TEST_ASSERT(!kvm_has_gmem_attributes || > + src_type == VM_MEM_SRC_SHMEM, > + "Testing in-place conversions, only %s > mem_type supported\n", > + > vm_mem_backing_src_alias(VM_MEM_SRC_SHMEM)->name); > break; > case 'n': > nr_vcpus = atoi_positive("nr_vcpus", optarg); > > -- > 2.55.0.rc0.738.g0c8ab3ebcc-goog > >
