linux-kernel - [PATCH v6 2/2] RISC-V: KVM: selftests: Add RISC-V SBI STA shmem alignment tests

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Message-Id: <20260205010502.2554381-3-xujiakai2025@iscas.ac.cn>
Date: Thu,  5 Feb 2026 01:05:02 +0000
From: Jiakai Xu <xujiakai2025@...as.ac.cn>
To: linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	kvm-riscv@...ts.infradead.org,
	linux-riscv@...ts.infradead.org,
	linux-kselftest@...r.kernel.org
Cc: Anup Patel <anup@...infault.org>,
	Atish Patra <atish.patra@...ux.dev>,
	Paul Walmsley <pjw@...nel.org>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Alexandre Ghiti <alex@...ti.fr>,
	Andrew Jones <ajones@...tanamicro.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Shuah Khan <shuah@...nel.org>,
	Jiakai Xu <xujiakai2025@...as.ac.cn>,
	Jiakai Xu <jiakaiPeanut@...il.com>
Subject: [PATCH v6 2/2] RISC-V: KVM: selftests: Add RISC-V SBI STA shmem alignment tests

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
- INVALID_GPA correctly disables steal-time accounting

Signed-off-by: Jiakai Xu <xujiakai2025@...as.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut@...il.com>
---
 .../selftests/kvm/include/riscv/processor.h   |  4 +++
 tools/testing/selftests/kvm/steal_time.c      | 33 +++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/riscv/processor.h b/tools/testing/selftests/kvm/include/riscv/processor.h
index e58282488beb3..c3551d129d2f6 100644
--- a/tools/testing/selftests/kvm/include/riscv/processor.h
+++ b/tools/testing/selftests/kvm/include/riscv/processor.h
@@ -62,6 +62,10 @@ static inline uint64_t __kvm_reg_id(uint64_t type, uint64_t subtype,
 						     KVM_REG_RISCV_SBI_SINGLE,		\
 						     idx, KVM_REG_SIZE_ULONG)
 
+#define RISCV_SBI_STA_REG(idx)	__kvm_reg_id(KVM_REG_RISCV_SBI_STATE,	\
+						     KVM_REG_RISCV_SBI_STA,			\
+						     idx, KVM_REG_SIZE_ULONG)
+
 bool __vcpu_has_ext(struct kvm_vcpu *vcpu, uint64_t ext);
 
 static inline bool __vcpu_has_isa_ext(struct kvm_vcpu *vcpu, uint64_t isa_ext)
diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index 8edc1fca345ba..30b98d1b601c3 100644
--- a/tools/testing/selftests/kvm/steal_time.c
+++ b/tools/testing/selftests/kvm/steal_time.c
@@ -209,6 +209,7 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
 
 /* SBI STA shmem must have 64-byte alignment */
 #define STEAL_TIME_SIZE		((sizeof(struct sta_struct) + 63) & ~63)
+#define INVALID_GPA (~(u64)0)
 
 static vm_paddr_t st_gpa[NR_VCPUS];
 
@@ -301,6 +302,34 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
 	pr_info("\n");
 }
 
+static void test_riscv_sta_shmem_alignment(struct kvm_vcpu *vcpu)
+{
+	struct kvm_one_reg reg;
+	uint64_t shmem;
+	int ret;
+
+	reg.id = RISCV_SBI_STA_REG(0);
+	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 should return -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 should succeed");
+
+	/* Case 3: INVALID_GPA disables STA */
+	shmem = INVALID_GPA;
+	ret = __vcpu_ioctl(vcpu, KVM_SET_ONE_REG, &reg);
+	TEST_ASSERT(ret == 0,
+		    "INVALID_GPA should disable STA successfully");
+}
+
 #endif
 
 static void *do_steal_time(void *arg)
@@ -369,6 +398,10 @@ int main(int ac, char **av)
 	TEST_REQUIRE(is_steal_time_supported(vcpus[0]));
 	ksft_set_plan(NR_VCPUS);
 
+#ifdef __riscv
+	test_riscv_sta_shmem_alignment(vcpus[0]);
+#endif
+
 	/* Run test on each VCPU */
 	for (i = 0; i < NR_VCPUS; ++i) {
 		steal_time_init(vcpus[i], i);
-- 
2.34.1