[PATCH v9 3/3] RISC-V: KVM: selftests: Add RISC-V SBI STA shmem alignment tests

[Jiakai Xu]

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 <xujiakai2025 at iscas.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut at gmail.com>
---
V8 -> V9: Dropped __riscv guard around INVALID_GPA, which is common to
           all architectures.
V7 -> V8: Moved INVALID_GPA definition to kvm_util_types.h.
          Removed comments in RISC-V check_steal_time_uapi().
          Corrected reg.id assignment for SBI STA.
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)
---
 .../selftests/kvm/include/kvm_util_types.h    |  2 ++
 tools/testing/selftests/kvm/steal_time.c      | 31 +++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_types.h b/tools/testing/selftests/kvm/include/kvm_util_types.h
index ec787b97cf184..0366e9bce7f93 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_types.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_types.h
@@ -17,4 +17,6 @@
 typedef uint64_t vm_paddr_t; /* Virtual Machine (Guest) physical address */
 typedef uint64_t vm_vaddr_t; /* Virtual Machine (Guest) virtual address */
 
+#define INVALID_GPA (~(uint64_t)0)
+
 #endif /* SELFTEST_KVM_UTIL_TYPES_H */
diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index 75ad067f27260..0708b94ead895 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -332,6 +332,37 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
 
 static void check_steal_time_uapi()
 {
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	struct kvm_one_reg reg;
+	uint64_t shmem;
+	int ret;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	reg.id = KVM_REG_RISCV |
+			 KVM_REG_SIZE_ULONG |
+			 KVM_REG_RISCV_SBI_STATE |
+			 KVM_REG_RISCV_SBI_STA |
+			 KVM_REG_RISCV_SBI_STA_REG(shmem_lo);
+	reg.addr = (uint64_t)&shmem;
+
+	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");
+
+	shmem = ST_GPA_BASE;
+	ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
+	TEST_ASSERT(ret == 0,
+		    "aligned STA shmem succeeds");
+
+	shmem = INVALID_GPA;
+	ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
+	TEST_ASSERT(ret == 0,
+		    "all-ones for STA shmem succeeds");
+
+	kvm_vm_free(vm);
 }
 
 #endif
-- 
2.34.1