Re: [PATCH v7 3/3] RISC-V: KVM: selftests: Add RISC-V SBI STA shmem alignment tests

[Andrew Jones]

On Fri, Feb 13, 2026 at 10:35:57AM +0000, Jiakai Xu wrote:
> Add RISC-V KVM selftests to verify the SBI Steal-Time Accounting (STA)
> shared memory alignment requirements.
> 
> The SBI specification requires the STA shared memory GPA to be 64-byte
> aligned, or set to all-ones to explicitly disable steal-time accounting.
> This test verifies that KVM enforces the expected behavior when
> configuring the SBI STA shared memory via KVM_SET_ONE_REG.
> 
> Specifically, the test checks that:
> - misaligned GPAs are rejected with -EINVAL
> - 64-byte aligned GPAs are accepted
> - all-ones GPA is accepted
> 
> Signed-off-by: Jiakai Xu <xujiakai2...@iscas.ac.cn>
> Signed-off-by: Jiakai Xu <jiakaipea...@gmail.com>
> ---
> V6 -> V7: 
> - Removed RISCV_SBI_STA_REG() macro addition and used existing 
> KVM_REG_RISCV_SBI_STA_REG(shmem_lo) instead.
> - Refined assertion messages per review feedback.
> - Split into two patches per Andrew Jones' suggestion:
>     Refactored UAPI tests from steal_time_init() into dedicated 
>     check_steal_time_uapi() function and added empty stub for 
>     RISC-V.
>     Filled in RISC-V stub with STA alignment tests. (this patch)
> ---
>  tools/testing/selftests/kvm/steal_time.c | 26 +++++++++++++++++++++++-
>  1 file changed, 25 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/kvm/steal_time.c 
> b/tools/testing/selftests/kvm/steal_time.c
> index a814f6f3f8b41..2af7fd7513d55 100644
> --- a/tools/testing/selftests/kvm/steal_time.c
> +++ b/tools/testing/selftests/kvm/steal_time.c
> @@ -233,6 +233,7 @@ static void check_steal_time_uapi(struct kvm_vcpu *vcpu)
>  
>  /* SBI STA shmem must have 64-byte alignment */
>  #define STEAL_TIME_SIZE              ((sizeof(struct sta_struct) + 63) & ~63)
> +#define INVALID_GPA (~(u64)0)

This belongs in kvm_util_types.h

>  
>  static vm_paddr_t st_gpa[NR_VCPUS];
>  
> @@ -327,7 +328,30 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t 
> vcpu_idx)
>  
>  static void check_steal_time_uapi(struct kvm_vcpu *vcpu)
>  {
> -     /* RISC-V UAPI tests will be added in a subsequent patch */
> +     struct kvm_one_reg reg;
> +     uint64_t shmem;
> +     int ret;
> +
> +     reg.id = KVM_REG_RISCV_SBI_STA_REG(shmem_lo);
> +     reg.addr = (uint64_t)&shmem;
> +
> +     /* Case 1: misaligned GPA */
> +     shmem = ST_GPA_BASE + 1;
> +     ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
> +     TEST_ASSERT(ret == -1 && errno == EINVAL,
> +                 "misaligned STA shmem returns -EINVAL");
> +
> +     /* Case 2: 64-byte aligned GPA */
> +     shmem = ST_GPA_BASE;
> +     ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
> +     TEST_ASSERT(ret == 0,
> +                 "aligned STA shmem succeeds");
> +
> +     /* Case 3: INVALID_GPA disables STA */
> +     shmem = INVALID_GPA;
> +     ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
> +     TEST_ASSERT(ret == 0,
> +                 "all-ones for STA shmem succeeds");
>  }

I'd remove the 'Case 1', 'Case 2', text from the comments because it'll
be a pain to maintain when people want to add/remove test cases.

Thanks,
drew