Add a selftest (arm64/hdbss_test) for the KVM_CAP_ARM_HDBSS_BUFFER_SIZE interface: CHECK_EXTENSION semantics (global max, per-VM default and configured values), the accepted size range (power of two in [PAGE_SIZE, SZ_2M]), the rejection paths (invalid sizes, after vCPU creation, duplicate configuration, dirty ring enabled), and the contract that enabling the dirty ring resets a configured size to the default.
The default size is derived from getpagesize() so the test holds on 16KB/64KB page systems. The test does not run guest code. Signed-off-by: Tian Zheng <[email protected]> --- tools/testing/selftests/kvm/Makefile.kvm | 1 + .../testing/selftests/kvm/arm64/hdbss_test.c | 224 ++++++++++++++++++ 2 files changed, 225 insertions(+) create mode 100644 tools/testing/selftests/kvm/arm64/hdbss_test.c diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm index 6a1482e3a286..a665fd568391 100644 --- a/tools/testing/selftests/kvm/Makefile.kvm +++ b/tools/testing/selftests/kvm/Makefile.kvm @@ -179,6 +179,7 @@ TEST_GEN_PROGS_arm64 += arm64/hello_el2 TEST_GEN_PROGS_arm64 += arm64/host_sve TEST_GEN_PROGS_arm64 += arm64/hypercalls TEST_GEN_PROGS_arm64 += arm64/external_aborts +TEST_GEN_PROGS_arm64 += arm64/hdbss_test TEST_GEN_PROGS_arm64 += arm64/mmio_sign_ext TEST_GEN_PROGS_arm64 += arm64/page_fault_test TEST_GEN_PROGS_arm64 += arm64/psci_test diff --git a/tools/testing/selftests/kvm/arm64/hdbss_test.c b/tools/testing/selftests/kvm/arm64/hdbss_test.c new file mode 100644 index 000000000000..9de26d2a67d1 --- /dev/null +++ b/tools/testing/selftests/kvm/arm64/hdbss_test.c @@ -0,0 +1,224 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Test the KVM_CAP_ARM_HDBSS_BUFFER_SIZE ioctl interface: query + * semantics, accepted/rejected sizes, and the interaction with the + * dirty ring. Does not run guest code. + * + * Copyright (C) 2026 Huawei Technologies Co., Ltd + * Author: Tian Zheng <[email protected]> + */ + +#include <errno.h> +#include <linux/sizes.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#include "kvm_util.h" +#include "test_util.h" + +/* + * The kernel default is PAGE_SIZE: derive it from the running kernel so + * the test also holds on 16KB/64KB page systems. + */ +#define HDBSS_DEFAULT_SIZE ((u64)getpagesize()) +#define HDBSS_MAX_SIZE SZ_2M + +static bool hdbss_supported(void) +{ + return kvm_check_cap(KVM_CAP_ARM_HDBSS_BUFFER_SIZE) > 0; +} + +static long hdbss_global_query(void) +{ + return (long)kvm_check_cap(KVM_CAP_ARM_HDBSS_BUFFER_SIZE); +} + +static long hdbss_vm_query(struct kvm_vm *vm) +{ + return (long)vm_check_cap(vm, KVM_CAP_ARM_HDBSS_BUFFER_SIZE); +} + +static int hdbss_set(struct kvm_vm *vm, u64 size) +{ + return __vm_enable_cap(vm, KVM_CAP_ARM_HDBSS_BUFFER_SIZE, size); +} + +static void test_global_query(void) +{ + long ret; + + ret = hdbss_global_query(); + TEST_ASSERT(ret == HDBSS_MAX_SIZE, + "Global HDBSS query returned %ld (0x%lx), expected %d (0x%x)", + ret, ret, HDBSS_MAX_SIZE, HDBSS_MAX_SIZE); + pr_info("Global HDBSS max size: %ld bytes\n", ret); +} + +static void test_vm_query_default(void) +{ + struct kvm_vm *vm; + long ret; + + vm = vm_create_barebones(); + ret = hdbss_vm_query(vm); + TEST_ASSERT(ret == HDBSS_DEFAULT_SIZE, + "Per-VM HDBSS query (unconfigured) returned %ld, expected %ld", + ret, (long)HDBSS_DEFAULT_SIZE); + pr_info("Default HDBSS buffer size: %ld bytes\n", ret); + kvm_vm_free(vm); +} + +static void test_vm_query_after_set(u64 set_size) +{ + struct kvm_vm *vm; + long ret; + + vm = vm_create_barebones(); + TEST_ASSERT_EQ(hdbss_set(vm, set_size), 0); + ret = hdbss_vm_query(vm); + TEST_ASSERT(ret == (long)set_size, + "Per-VM HDBSS query after set returned %ld, expected %lld", + ret, (unsigned long long)set_size); + kvm_vm_free(vm); +} + +static void test_set_valid(u64 size) +{ + struct kvm_vm *vm; + int ret; + + vm = vm_create_barebones(); + ret = hdbss_set(vm, size); + TEST_ASSERT(ret == 0, + "Setting HDBSS buffer size to %lld (0x%llx) failed: %d (%s)", + (unsigned long long)size, (unsigned long long)size, + ret, strerror(errno)); + pr_info("Set HDBSS buffer size to %lld bytes: OK\n", + (unsigned long long)size); + kvm_vm_free(vm); +} + +static void test_set_invalid(u64 size, int expected_errno) +{ + struct kvm_vm *vm; + int ret; + + vm = vm_create_barebones(); + ret = hdbss_set(vm, size); + TEST_ASSERT(ret == -1 && errno == expected_errno, + "HDBSS buffer size set to %lld (0x%llx) should fail with %d, got ret=%d errno=%d (%s)", + (unsigned long long)size, (unsigned long long)size, + expected_errno, ret, errno, strerror(errno)); + kvm_vm_free(vm); +} + +static void test_set_after_vcpu(void) +{ + struct kvm_vm *vm; + int ret; + + vm = vm_create_barebones(); + __vm_vcpu_add(vm, 0); + ret = hdbss_set(vm, HDBSS_DEFAULT_SIZE); + TEST_ASSERT(ret == -1 && errno == EINVAL, + "Setting HDBSS buffer size after vCPU creation should fail with EINVAL, got ret=%d errno=%d", + ret, errno); + pr_info("Set HDBSS after vCPU creation: correctly rejected\n"); + kvm_vm_free(vm); +} + +static void test_set_twice(void) +{ + struct kvm_vm *vm; + int ret; + + vm = vm_create_barebones(); + TEST_ASSERT_EQ(hdbss_set(vm, HDBSS_DEFAULT_SIZE), 0); + ret = hdbss_set(vm, HDBSS_DEFAULT_SIZE * 2); + TEST_ASSERT(ret == -1 && errno == EBUSY, + "Duplicate HDBSS buffer size set should fail with EBUSY, got ret=%d errno=%d", + ret, errno); + pr_info("Duplicate HDBSS set: correctly rejected\n"); + kvm_vm_free(vm); +} + +static void test_mutex_dirty_ring_then_hdbss(void) +{ + struct kvm_vm *vm; + int ret; + + vm = vm_create_barebones(); + + /* Sized to cover the HDBSS reservation on any page size. */ + vm_enable_dirty_ring(vm, 16384 * sizeof(struct kvm_dirty_gfn)); + + ret = hdbss_set(vm, HDBSS_DEFAULT_SIZE); + TEST_ASSERT(ret == -1 && errno == EINVAL, + "Setting HDBSS after dirty ring should fail with EINVAL, got ret=%d errno=%d", + ret, errno); + pr_info("HDBSS after dirty ring: correctly rejected\n"); + kvm_vm_free(vm); +} + +static void test_dirty_ring_resets_size(void) +{ + struct kvm_vm *vm; + long ret; + + vm = vm_create_barebones(); + + /* + * The ring must cover the HDBSS reservation, 2 * buffer + 1KB. + * Ring mode then pins the buffer to the default. + */ + TEST_ASSERT_EQ(hdbss_set(vm, SZ_256K), 0); + vm_enable_dirty_ring(vm, 65536 * sizeof(struct kvm_dirty_gfn)); + ret = hdbss_vm_query(vm); + TEST_ASSERT(ret == (long)HDBSS_DEFAULT_SIZE, + "Dirty ring mode should reset the HDBSS buffer size to the default (%lld), got %ld", + (unsigned long long)HDBSS_DEFAULT_SIZE, ret); + pr_info("Dirty ring mode resets HDBSS buffer size to default\n"); + kvm_vm_free(vm); +} + +int main(void) +{ + /* + * Valid sizes depend on the page size: the kernel minimum is + * PAGE_SIZE, so only exercise sizes at or above it. + */ + u64 page_size = getpagesize(); + + TEST_REQUIRE(hdbss_supported()); + + pr_info("Starting HDBSS ioctl interface tests\n\n"); + + test_global_query(); + test_vm_query_default(); + if (page_size < SZ_16K) + test_vm_query_after_set(SZ_16K); + test_vm_query_after_set(HDBSS_MAX_SIZE); + + test_set_valid(HDBSS_DEFAULT_SIZE); + if (page_size < SZ_8K) + test_set_valid(SZ_8K); + if (page_size < SZ_64K) + test_set_valid(SZ_64K); + test_set_valid(HDBSS_MAX_SIZE); + + test_set_invalid(0, EINVAL); + test_set_invalid(3, EINVAL); + test_set_invalid(page_size - 1, EINVAL); + test_set_invalid(page_size + 1, EINVAL); + test_set_invalid(HDBSS_MAX_SIZE * 2, EINVAL); + + test_set_after_vcpu(); + test_set_twice(); + test_mutex_dirty_ring_then_hdbss(); + test_dirty_ring_resets_size(); + + pr_info("\nAll HDBSS ioctl interface tests passed!\n"); + return 0; +} -- 2.43.0
