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SubjectRe: [PATCH v6 8/9] selftests: KVM: aarch64: Introduce hypercall ABI test
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Hi Raghavendra,

On 4/27/22 12:59 AM, Raghavendra Rao Ananta wrote:
> On Tue, Apr 26, 2022 at 12:50 AM Gavin Shan <gshan@redhat.com> wrote:
>> On 4/23/22 8:03 AM, Raghavendra Rao Ananta wrote:
>>> Introduce a KVM selftest to check the hypercall interface
>>> for arm64 platforms. The test validates the user-space'
>>> [GET|SET]_ONE_REG interface to read/write the psuedo-firmware
>>> registers as well as its effects on the guest upon certain
>>> configurations.
>>>
>>> Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
>>> ---
>>> tools/testing/selftests/kvm/.gitignore | 1 +
>>> tools/testing/selftests/kvm/Makefile | 1 +
>>> .../selftests/kvm/aarch64/hypercalls.c | 335 ++++++++++++++++++
>>> 3 files changed, 337 insertions(+)
>>> create mode 100644 tools/testing/selftests/kvm/aarch64/hypercalls.c
>>>
>>
>> There are comments about @false_hvc_info[] and some nits, as below.
>> Please evaluate and improve if it makes sense to you. Otherwise, it
>> looks good to me:
>>
>> Reviewed-by: Gavin Shan <gshan@redhat.com>
>>
>>> diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
>>> index 1bb575dfc42e..b17e464ec661 100644
>>> --- a/tools/testing/selftests/kvm/.gitignore
>>> +++ b/tools/testing/selftests/kvm/.gitignore
>>> @@ -2,6 +2,7 @@
>>> /aarch64/arch_timer
>>> /aarch64/debug-exceptions
>>> /aarch64/get-reg-list
>>> +/aarch64/hypercalls
>>> /aarch64/psci_test
>>> /aarch64/vcpu_width_config
>>> /aarch64/vgic_init
>>> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
>>> index c2cf4d318296..97eef0c03d3b 100644
>>> --- a/tools/testing/selftests/kvm/Makefile
>>> +++ b/tools/testing/selftests/kvm/Makefile
>>> @@ -105,6 +105,7 @@ TEST_GEN_PROGS_x86_64 += system_counter_offset_test
>>> TEST_GEN_PROGS_aarch64 += aarch64/arch_timer
>>> TEST_GEN_PROGS_aarch64 += aarch64/debug-exceptions
>>> TEST_GEN_PROGS_aarch64 += aarch64/get-reg-list
>>> +TEST_GEN_PROGS_aarch64 += aarch64/hypercalls
>>> TEST_GEN_PROGS_aarch64 += aarch64/psci_test
>>> TEST_GEN_PROGS_aarch64 += aarch64/vcpu_width_config
>>> TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
>>> diff --git a/tools/testing/selftests/kvm/aarch64/hypercalls.c b/tools/testing/selftests/kvm/aarch64/hypercalls.c
>>> new file mode 100644
>>> index 000000000000..f404343a0ae3
>>> --- /dev/null
>>> +++ b/tools/testing/selftests/kvm/aarch64/hypercalls.c
>>> @@ -0,0 +1,335 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +
>>> +/* hypercalls: Check the ARM64's psuedo-firmware bitmap register interface.
>>> + *
>>> + * The test validates the basic hypercall functionalities that are exposed
>>> + * via the psuedo-firmware bitmap register. This includes the registers'
>>> + * read/write behavior before and after the VM has started, and if the
>>> + * hypercalls are properly masked or unmasked to the guest when disabled or
>>> + * enabled from the KVM userspace, respectively.
>>> + */
>>> +
>>> +#include <errno.h>
>>> +#include <linux/arm-smccc.h>
>>> +#include <asm/kvm.h>
>>> +#include <kvm_util.h>
>>> +
>>> +#include "processor.h"
>>> +
>>> +#define FW_REG_ULIMIT_VAL(max_feat_bit) (GENMASK(max_feat_bit, 0))
>>> +
>>> +/* Last valid bits of the bitmapped firmware registers */
>>> +#define KVM_REG_ARM_STD_BMAP_BIT_MAX 0
>>> +#define KVM_REG_ARM_STD_HYP_BMAP_BIT_MAX 0
>>> +#define KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_MAX 1
>>> +
>>> +struct kvm_fw_reg_info {
>>> + uint64_t reg; /* Register definition */
>>> + uint64_t max_feat_bit; /* Bit that represents the upper limit of the feature-map */
>>> +};
>>> +
>>> +#define FW_REG_INFO(r) \
>>> + { \
>>> + .reg = r, \
>>> + .max_feat_bit = r##_BIT_MAX, \
>>> + }
>>> +
>>> +static const struct kvm_fw_reg_info fw_reg_info[] = {
>>> + FW_REG_INFO(KVM_REG_ARM_STD_BMAP),
>>> + FW_REG_INFO(KVM_REG_ARM_STD_HYP_BMAP),
>>> + FW_REG_INFO(KVM_REG_ARM_VENDOR_HYP_BMAP),
>>> +};
>>> +
>>> +enum test_stage {
>>> + TEST_STAGE_REG_IFACE,
>>> + TEST_STAGE_HVC_IFACE_FEAT_DISABLED,
>>> + TEST_STAGE_HVC_IFACE_FEAT_ENABLED,
>>> + TEST_STAGE_HVC_IFACE_FALSE_INFO,
>>> + TEST_STAGE_END,
>>> +};
>>> +
>>> +static int stage = TEST_STAGE_REG_IFACE;
>>> +
>>> +struct test_hvc_info {
>>> + uint32_t func_id;
>>> + uint64_t arg1;
>>> +};
>>> +
>>> +#define TEST_HVC_INFO(f, a1) \
>>> + { \
>>> + .func_id = f, \
>>> + .arg1 = a1, \
>>> + }
>>> +
>>> +static const struct test_hvc_info hvc_info[] = {
>>> + /* KVM_REG_ARM_STD_BMAP */
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_VERSION, 0),
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_TRNG_RND64),
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_GET_UUID, 0),
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_RND32, 0),
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_RND64, 0),
>>> +
>>> + /* KVM_REG_ARM_STD_HYP_BMAP */
>>> + TEST_HVC_INFO(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_HV_PV_TIME_FEATURES),
>>> + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_FEATURES, ARM_SMCCC_HV_PV_TIME_ST),
>>> + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_ST, 0),
>>> +
>>> + /* KVM_REG_ARM_VENDOR_HYP_BMAP */
>>> + TEST_HVC_INFO(ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID,
>>> + ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID),
>>> + TEST_HVC_INFO(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, 0),
>>> + TEST_HVC_INFO(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID, KVM_PTP_VIRT_COUNTER),
>>> +};
>>> +
>>> +/* Feed false hypercall info to test the KVM behavior */
>>> +static const struct test_hvc_info false_hvc_info[] = {
>>> + /* Feature support check against a different family of hypercalls */
>>> + TEST_HVC_INFO(ARM_SMCCC_TRNG_FEATURES, ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID),
>>> + TEST_HVC_INFO(ARM_SMCCC_ARCH_FEATURES_FUNC_ID, ARM_SMCCC_TRNG_RND64),
>>> + TEST_HVC_INFO(ARM_SMCCC_HV_PV_TIME_FEATURES, ARM_SMCCC_TRNG_RND64),
>>> +};
>>> +
>>
>> I don't see too much benefits of @false_hvc_info[] because
>> NOT_SUPPORTED is always returned from its test case. I think
>> it and its test case can be removed if you agree. I'm not
>> sure if it was suggested by somebody else.
>>
> While this is not exactly testing the bitmap firmware registers, the
> idea behind introducing false_hvc_info[] was to introduce some
> negative tests and see if KVM handles it well. Especially with
> *_FEATURES func_ids, we can accidentally introduce functional bugs in
> KVM, and these would act as our safety net. I was planning to also
> test with some reserved hypercall numbers, just to test if the kernel
> doesn't panic for some reason.
>

Ok, thanks for the explanation. It makes sense to me.

>>> +static void guest_test_hvc(const struct test_hvc_info *hc_info)
>>> +{
>>> + unsigned int i;
>>> + struct arm_smccc_res res;
>>> + unsigned int hvc_info_arr_sz;
>>> +
>>> + hvc_info_arr_sz =
>>> + hc_info == hvc_info ? ARRAY_SIZE(hvc_info) : ARRAY_SIZE(false_hvc_info);
>>> +
>>> + for (i = 0; i < hvc_info_arr_sz; i++, hc_info++) {
>>> + memset(&res, 0, sizeof(res));
>>> + smccc_hvc(hc_info->func_id, hc_info->arg1, 0, 0, 0, 0, 0, 0, &res);
>>> +
>>> + switch (stage) {
>>> + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
>>> + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
>>> + GUEST_ASSERT_3(res.a0 == SMCCC_RET_NOT_SUPPORTED,
>>> + res.a0, hc_info->func_id, hc_info->arg1);
>>> + break;
>>> + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
>>> + GUEST_ASSERT_3(res.a0 != SMCCC_RET_NOT_SUPPORTED,
>>> + res.a0, hc_info->func_id, hc_info->arg1);
>>> + break;
>>> + default:
>>> + GUEST_ASSERT_1(0, stage);
>>> + }
>>> + }
>>> +}
>>> +
>>> +static void guest_code(void)
>>> +{
>>> + while (stage != TEST_STAGE_END) {
>>> + switch (stage) {
>>> + case TEST_STAGE_REG_IFACE:
>>> + break;
>>> + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
>>> + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
>>> + guest_test_hvc(hvc_info);
>>> + break;
>>> + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
>>> + guest_test_hvc(false_hvc_info);
>>> + break;
>>> + default:
>>> + GUEST_ASSERT_1(0, stage);
>>> + }
>>> +
>>> + GUEST_SYNC(stage);
>>> + }
>>> +
>>> + GUEST_DONE();
>>> +}
>>> +
>>> +static int set_fw_reg(struct kvm_vm *vm, uint64_t id, uint64_t val)
>>> +{
>>> + struct kvm_one_reg reg = {
>>> + .id = id,
>>> + .addr = (uint64_t)&val,
>>> + };
>>> +
>>> + return _vcpu_ioctl(vm, 0, KVM_SET_ONE_REG, &reg);
>>> +}
>>> +
>>> +static void get_fw_reg(struct kvm_vm *vm, uint64_t id, uint64_t *addr)
>>> +{
>>> + struct kvm_one_reg reg = {
>>> + .id = id,
>>> + .addr = (uint64_t)addr,
>>> + };
>>> +
>>> + vcpu_ioctl(vm, 0, KVM_GET_ONE_REG, &reg);
>>> +}
>>> +
>>> +struct st_time {
>>> + uint32_t rev;
>>> + uint32_t attr;
>>> + uint64_t st_time;
>>> +};
>>> +
>>> +#define STEAL_TIME_SIZE ((sizeof(struct st_time) + 63) & ~63)
>>> +#define ST_GPA_BASE (1 << 30)
>>> +
>>> +static void steal_time_init(struct kvm_vm *vm)
>>> +{
>>> + uint64_t st_ipa = (ulong)ST_GPA_BASE;
>>> + unsigned int gpages;
>>> + struct kvm_device_attr dev = {
>>> + .group = KVM_ARM_VCPU_PVTIME_CTRL,
>>> + .attr = KVM_ARM_VCPU_PVTIME_IPA,
>>> + .addr = (uint64_t)&st_ipa,
>>> + };
>>> +
>>> + gpages = vm_calc_num_guest_pages(VM_MODE_DEFAULT, STEAL_TIME_SIZE);
>>> + vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, ST_GPA_BASE, 1, gpages, 0);
>>> +
>>> + vcpu_ioctl(vm, 0, KVM_SET_DEVICE_ATTR, &dev);
>>> +}
>>> +
>>> +static void test_fw_regs_before_vm_start(struct kvm_vm *vm)
>>> +{
>>> + uint64_t val;
>>> + unsigned int i;
>>> + int ret;
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(fw_reg_info); i++) {
>>> + const struct kvm_fw_reg_info *reg_info = &fw_reg_info[i];
>>> +
>>> + /* First 'read' should be an upper limit of the features supported */
>>> + get_fw_reg(vm, reg_info->reg, &val);
>>> + TEST_ASSERT(val == FW_REG_ULIMIT_VAL(reg_info->max_feat_bit),
>>> + "Expected all the features to be set for reg: 0x%lx; expected: 0x%lx; read: 0x%lx\n",
>>> + reg_info->reg, FW_REG_ULIMIT_VAL(reg_info->max_feat_bit), val);
>>> +
>>> + /* Test a 'write' by disabling all the features of the register map */
>>> + ret = set_fw_reg(vm, reg_info->reg, 0);
>>> + TEST_ASSERT(ret == 0,
>>> + "Failed to clear all the features of reg: 0x%lx; ret: %d\n",
>>> + reg_info->reg, errno);
>>> +
>>> + get_fw_reg(vm, reg_info->reg, &val);
>>> + TEST_ASSERT(val == 0,
>>> + "Expected all the features to be cleared for reg: 0x%lx\n", reg_info->reg);
>>> +
>>> + /*
>>> + * Test enabling a feature that's not supported.
>>> + * Avoid this check if all the bits are occupied.
>>> + */
>>> + if (reg_info->max_feat_bit < 63) {
>>> + ret = set_fw_reg(vm, reg_info->reg, BIT(reg_info->max_feat_bit + 1));
>>> + TEST_ASSERT(ret != 0 && errno == EINVAL,
>>> + "Unexpected behavior or return value (%d) while setting an unsupported feature for reg: 0x%lx\n",
>>> + errno, reg_info->reg);
>>> + }
>>> + }
>>> +}
>>
>> Just in case :)
>>
>> ret = set_fw_reg(vm, reg_info->reg, GENMASK(63, reg_info->max_feat_bit + 1));
>>
> It may be better to cover the entire range, but to test only the
> (max_feat_bit + 1) gives us the advantage of checking if there's any
> discrepancy between the kernel and the test, now that *_BIT_MAX are
> not a part of UAPI headers.
>
> Probably also include your test along with the existing one?

Thanks for your explanation again. Lets keep it as it is then.

>>
>>> +
>>> +static void test_fw_regs_after_vm_start(struct kvm_vm *vm)
>>> +{
>>> + uint64_t val;
>>> + unsigned int i;
>>> + int ret;
>>> +
>>> + for (i = 0; i < ARRAY_SIZE(fw_reg_info); i++) {
>>> + const struct kvm_fw_reg_info *reg_info = &fw_reg_info[i];
>>> +
>>> + /*
>>> + * Before starting the VM, the test clears all the bits.
>>> + * Check if that's still the case.
>>> + */
>>> + get_fw_reg(vm, reg_info->reg, &val);
>>> + TEST_ASSERT(val == 0,
>>> + "Expected all the features to be cleared for reg: 0x%lx\n",
>>> + reg_info->reg);
>>> +
>>> + /*
>>> + * Set all the features for this register again. KVM shouldn't
>>> + * allow this as the VM is running.
>>> + */
>>> + ret = set_fw_reg(vm, reg_info->reg, FW_REG_ULIMIT_VAL(reg_info->max_feat_bit));
>>> + TEST_ASSERT(ret != 0 && errno == EBUSY,
>>> + "Unexpected behavior or return value (%d) while setting a feature while VM is running for reg: 0x%lx\n",
>>> + errno, reg_info->reg);
>>> + }
>>> +}
>>> +
>>
>> I guess you want to check -EBUSY is returned. In that case,
>> the comments here could be clearer, something like below
>> to emphasize '-EBUSY'.
>>
>> /*
>> * After VM runs for once, -EBUSY should be returned on attempt
>> * to set features. Check if the correct errno is returned.
>> */
>>
> Sounds good.
>
>>> +static struct kvm_vm *test_vm_create(void)
>>> +{
>>> + struct kvm_vm *vm;
>>> +
>>> + vm = vm_create_default(0, 0, guest_code);
>>> +
>>> + ucall_init(vm, NULL);
>>> + steal_time_init(vm);
>>> +
>>> + return vm;
>>> +}
>>> +
>>> +static struct kvm_vm *test_guest_stage(struct kvm_vm *vm)
>>> +{
>>> + struct kvm_vm *ret_vm = vm;
>>> +
>>> + pr_debug("Stage: %d\n", stage);
>>> +
>>> + switch (stage) {
>>> + case TEST_STAGE_REG_IFACE:
>>> + test_fw_regs_after_vm_start(vm);
>>> + break;
>>> + case TEST_STAGE_HVC_IFACE_FEAT_DISABLED:
>>> + /* Start a new VM so that all the features are now enabled by default */
>>> + kvm_vm_free(vm);
>>> + ret_vm = test_vm_create();
>>> + break;
>>> + case TEST_STAGE_HVC_IFACE_FEAT_ENABLED:
>>> + case TEST_STAGE_HVC_IFACE_FALSE_INFO:
>>> + break;
>>> + default:
>>> + TEST_FAIL("Unknown test stage: %d\n", stage);
>>> + }
>>> +
>>> + stage++;
>>> + sync_global_to_guest(vm, stage);
>>> +
>>> + return ret_vm;
>>> +}
>>> +
>>> +static void test_run(void)
>>> +{
>>> + struct kvm_vm *vm;
>>> + struct ucall uc;
>>> + bool guest_done = false;
>>> +
>>> + vm = test_vm_create();
>>> +
>>> + test_fw_regs_before_vm_start(vm);
>>> +
>>> + while (!guest_done) {
>>> + vcpu_run(vm, 0);
>>> +
>>> + switch (get_ucall(vm, 0, &uc)) {
>>> + case UCALL_SYNC:
>>> + vm = test_guest_stage(vm);
>>> + break;
>>> + case UCALL_DONE:
>>> + guest_done = true;
>>> + break;
>>> + case UCALL_ABORT:
>>> + TEST_FAIL("%s at %s:%ld\n\tvalues: 0x%lx, 0x%lx; 0x%lx, stage: %u",
>>> + (const char *)uc.args[0], __FILE__, uc.args[1],
>>> + uc.args[2], uc.args[3], uc.args[4], stage);
>>> + break;
>>> + default:
>>> + TEST_FAIL("Unexpected guest exit\n");
>>> + }
>>> + }
>>> +
>>> + kvm_vm_free(vm);
>>> +}
>>> +
>>> +int main(void)
>>> +{
>>> + setbuf(stdout, NULL);
>>> +
>>> + test_run();
>>> + return 0;
>>> +}
>>>

[...]

Thanks,
Gavin

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