Re: [PATCH v7 2/3] KVM: selftests: Refactor UAPI tests into dedicated function

[Andrew Jones]

On Fri, Feb 13, 2026 at 10:35:56AM +0000, Jiakai Xu wrote:
> Move steal time UAPI tests from steal_time_init() into a separate
> check_steal_time_uapi() function for better code organization and
> maintainability.
> 
> Previously, x86 and ARM64 architectures performed UAPI validation
> tests within steal_time_init(), mixing initialization logic with
> uapi tests.
> 
> Changes by architecture:
> x86_64:
>   - Extract MSR reserved bits test from steal_time_init()
>   - Move to check_steal_time_uapi() which tests that setting
>     MSR_KVM_STEAL_TIME with KVM_STEAL_RESERVED_MASK fails
> ARM64:
>   - Extract three UAPI tests from steal_time_init():
>     	Device attribute support check
>     	Misaligned IPA rejection (EINVAL)
>     	Duplicate IPA setting rejection (EEXIST)
>   - Move all tests to check_steal_time_uapi()
> RISC-V:
>   - Add empty check_steal_time_uapi() stub for future use
>   - No changes to steal_time_init() (had no tests to extract)
> 
> The new check_steal_time_uapi() function:
>   - Is called once before the per-VCPU test loop
> 
> No functional change intended.
> 

Suggested-by: Andrew Jones <andrew.jones@xxxxxxxxxxxxxxxx>

> Signed-off-by: Jiakai Xu <xujiakai2025@xxxxxxxxxxx>
> Signed-off-by: Jiakai Xu <jiakaiPeanut@xxxxxxxxx>
> ---
>  tools/testing/selftests/kvm/steal_time.c | 63 ++++++++++++++++++------
>  1 file changed, 47 insertions(+), 16 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
> index 8edc1fca345ba..a814f6f3f8b41 100644
> --- a/tools/testing/selftests/kvm/steal_time.c
> +++ b/tools/testing/selftests/kvm/steal_time.c
> @@ -69,16 +69,10 @@ static bool is_steal_time_supported(struct kvm_vcpu *vcpu)
>  
>  static void steal_time_init(struct kvm_vcpu *vcpu, uint32_t i)
>  {
> -	int ret;
> -
>  	/* ST_GPA_BASE is identity mapped */
>  	st_gva[i] = (void *)(ST_GPA_BASE + i * STEAL_TIME_SIZE);
>  	sync_global_to_guest(vcpu->vm, st_gva[i]);
>  
> -	ret = _vcpu_set_msr(vcpu, MSR_KVM_STEAL_TIME,
> -			    (ulong)st_gva[i] | KVM_STEAL_RESERVED_MASK);
> -	TEST_ASSERT(ret == 0, "Bad GPA didn't fail");
> -
>  	vcpu_set_msr(vcpu, MSR_KVM_STEAL_TIME, (ulong)st_gva[i] | KVM_MSR_ENABLED);
>  }
>  
> @@ -99,6 +93,18 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
>  			st->pad[8], st->pad[9], st->pad[10]);
>  }
>  
> +static void check_steal_time_uapi(struct kvm_vcpu *vcpu)
> +{
> +	int ret;
> +
> +	st_gva[0] = (void *)(ST_GPA_BASE);
> +	sync_global_to_guest(vcpu->vm, st_gva[0]);

No need to use st_gva[] and sync_global_to_guest(). For this test we can
just use ST_GPA_BASE directly.

> +
> +	ret = _vcpu_set_msr(vcpu, MSR_KVM_STEAL_TIME,
> +			    (ulong)st_gva[0] | KVM_STEAL_RESERVED_MASK);
> +	TEST_ASSERT(ret == 0, "Bad GPA didn't fail");
> +}
> +
>  #elif defined(__aarch64__)
>  
>  /* PV_TIME_ST must have 64-byte alignment */
> @@ -170,7 +176,6 @@ static void steal_time_init(struct kvm_vcpu *vcpu, uint32_t i)
>  {
>  	struct kvm_vm *vm = vcpu->vm;
>  	uint64_t st_ipa;
> -	int ret;
>  
>  	struct kvm_device_attr dev = {
>  		.group = KVM_ARM_VCPU_PVTIME_CTRL,
> @@ -178,21 +183,12 @@ static void steal_time_init(struct kvm_vcpu *vcpu, uint32_t i)
>  		.addr = (uint64_t)&st_ipa,
>  	};
>  
> -	vcpu_ioctl(vcpu, KVM_HAS_DEVICE_ATTR, &dev);
> -
>  	/* ST_GPA_BASE is identity mapped */
>  	st_gva[i] = (void *)(ST_GPA_BASE + i * STEAL_TIME_SIZE);
>  	sync_global_to_guest(vm, st_gva[i]);
>  
> -	st_ipa = (ulong)st_gva[i] | 1;
> -	ret = __vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> -	TEST_ASSERT(ret == -1 && errno == EINVAL, "Bad IPA didn't report EINVAL");
> -
>  	st_ipa = (ulong)st_gva[i];
>  	vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> -
> -	ret = __vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> -	TEST_ASSERT(ret == -1 && errno == EEXIST, "Set IPA twice without EEXIST");
>  }
>  
>  static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
> @@ -205,6 +201,34 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
>  	ksft_print_msg("    st_time: %ld\n", st->st_time);
>  }
>  
> +static void check_steal_time_uapi(struct kvm_vcpu *vcpu)
> +{
> +	struct kvm_vm *vm = vcpu->vm;
> +	uint64_t st_ipa;
> +	int ret;
> +
> +	struct kvm_device_attr dev = {
> +		.group = KVM_ARM_VCPU_PVTIME_CTRL,
> +		.attr = KVM_ARM_VCPU_PVTIME_IPA,
> +		.addr = (uint64_t)&st_ipa,
> +	};
> +
> +	vcpu_ioctl(vcpu, KVM_HAS_DEVICE_ATTR, &dev);
> +
> +	st_gva[0] = (void *)(ST_GPA_BASE);
> +	sync_global_to_guest(vm, st_gva[0]);

Same comment as above.

> +
> +	st_ipa = (ulong)st_gva[0] | 1;
> +	ret = __vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> +	TEST_ASSERT(ret == -1 && errno == EINVAL, "Bad IPA didn't report EINVAL");
> +
> +	st_ipa = (ulong)st_gva[0];
> +	vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> +
> +	ret = __vcpu_ioctl(vcpu, KVM_SET_DEVICE_ATTR, &dev);
> +	TEST_ASSERT(ret == -1 && errno == EEXIST, "Set IPA twice without EEXIST");
> +}

Hmm... don't we now fail with EEXIST in arm64's steal_time_init() for i=0 ?
I think the only way to avoid it is to create a temporary vcpu for the uapi
tests which gets thrown away before creating the vcpus for the steal time
tests.

> +
>  #elif defined(__riscv)
>  
>  /* SBI STA shmem must have 64-byte alignment */
> @@ -301,6 +325,11 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
>  	pr_info("\n");
>  }
>  
> +static void check_steal_time_uapi(struct kvm_vcpu *vcpu)
> +{
> +	/* RISC-V UAPI tests will be added in a subsequent patch */

nit: no need for this comment.

> +}
> +
>  #endif
>  
>  static void *do_steal_time(void *arg)
> @@ -369,6 +398,8 @@ int main(int ac, char **av)
>  	TEST_REQUIRE(is_steal_time_supported(vcpus[0]));
>  	ksft_set_plan(NR_VCPUS);
>  
> +	check_steal_time_uapi(vcpus[0]);
> +
>  	/* Run test on each VCPU */
>  	for (i = 0; i < NR_VCPUS; ++i) {
>  		steal_time_init(vcpus[i], i);
> -- 
> 2.34.1
>

Thanks,
drew