[PATCH v9 0/3] RISC-V: KVM: Validate SBI STA shmem alignment

[PATCH v9 0/3] RISC-V: KVM: Validate SBI STA shmem alignment

[Jiakai Xu]

This series fixes a missing validation in the RISC-V KVM SBI
steal-time accounting (STA) register handling.

Patch 1 validates the configured SBI STA shared memory GPA at
KVM_SET_ONE_REG, enforcing the 64-byte alignment requirement
defined by the SBI specification or allowing INVALID_GPA to explicitly
disable steal-time accounting. This prevents invalid userspace state
from reaching runtime code paths and avoids WARN_ON() triggers during
KVM_RUN.

Patch 2 refactors existing UAPI tests from steal_time_init() into
a dedicated check_steal_time_uapi() function for better code organization,
and adds an empty stub for RISC-V.

Patch 3 fills in the RISC-V stub with tests that verify KVM correctly
enforces the STA alignment requirements.

Jiakai Xu (3):
  RISC-V: KVM: Validate SBI STA shmem alignment in 
    kvm_sbi_ext_sta_set_reg()
  KVM: selftests: Refactor UAPI tests into dedicated function
  RISC-V: KVM: selftests: Add RISC-V SBI STA shmem alignment tests

 arch/riscv/kvm/vcpu_sbi_sta.c                 | 16 ++-
 .../selftests/kvm/include/kvm_util_types.h    |  2 +
 tools/testing/selftests/kvm/steal_time.c      | 98 ++++++++++++++++---
 3 files changed, 95 insertions(+), 21 deletions(-)

-- 
2.34.1

[PATCH v9 1/3] RISC-V: KVM: Validate SBI STA shmem alignment in kvm_sbi_ext_sta_set_reg()

[Jiakai Xu]

The RISC-V SBI Steal-Time Accounting (STA) extension requires the shared
memory physical address to be 64-byte aligned, or set to all-ones to
explicitly disable steal-time accounting.

KVM exposes the SBI STA shared memory configuration to userspace via
KVM_SET_ONE_REG. However, the current implementation of
kvm_sbi_ext_sta_set_reg() does not validate the alignment of the configured
shared memory address. As a result, userspace can install a misaligned
shared memory address that violates the SBI specification.

Such an invalid configuration may later reach runtime code paths that
assume a valid and properly aligned shared memory region. In particular,
KVM_RUN can trigger the following WARN_ON in
kvm_riscv_vcpu_record_steal_time():

  WARNING: arch/riscv/kvm/vcpu_sbi_sta.c:49 at
  kvm_riscv_vcpu_record_steal_time

WARN_ON paths are not expected to be reachable during normal runtime
execution, and may result in a kernel panic when panic_on_warn is enabled.

Fix this by validating the computed shared memory GPA at the
KVM_SET_ONE_REG boundary. A temporary GPA is constructed and checked
before committing it to vcpu->arch.sta.shmem. The validation allows
either a 64-byte aligned GPA or INVALID_GPA (all-ones), which disables
STA as defined by the SBI specification.

This prevents invalid userspace state from reaching runtime code paths
that assume SBI STA invariants and avoids unexpected WARN_ON behavior.

Fixes: f61ce890b1f074 ("RISC-V: KVM: Add support for SBI STA registers")
Signed-off-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut@gmail.com>
Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>
---
V5 -> V6: Initialized new_shmem to INVALID_GPA as suggested.
V4 -> V5: Added parentheses to function name in subject.
V3 -> V4: Declared new_shmem at the top of kvm_sbi_ext_sta_set_reg().
          Initialized new_shmem to 0 instead of vcpu->arch.sta.shmem.
          Added blank lines per review feedback.
V2 -> V3: Added parentheses to function name in subject.
V1 -> V2: Added Fixes tag.
---
 arch/riscv/kvm/vcpu_sbi_sta.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
index afa0545c3bcfc..3b834709b429f 100644
--- a/arch/riscv/kvm/vcpu_sbi_sta.c
+++ b/arch/riscv/kvm/vcpu_sbi_sta.c
@@ -181,6 +181,7 @@ static int kvm_sbi_ext_sta_set_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
 				   unsigned long reg_size, const void *reg_val)
 {
 	unsigned long value;
+	gpa_t new_shmem = INVALID_GPA;
 
 	if (reg_size != sizeof(unsigned long))
 		return -EINVAL;
@@ -191,18 +192,18 @@ static int kvm_sbi_ext_sta_set_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
 		if (IS_ENABLED(CONFIG_32BIT)) {
 			gpa_t hi = upper_32_bits(vcpu->arch.sta.shmem);
 
-			vcpu->arch.sta.shmem = value;
-			vcpu->arch.sta.shmem |= hi << 32;
+			new_shmem = value;
+			new_shmem |= hi << 32;
 		} else {
-			vcpu->arch.sta.shmem = value;
+			new_shmem = value;
 		}
 		break;
 	case KVM_REG_RISCV_SBI_STA_REG(shmem_hi):
 		if (IS_ENABLED(CONFIG_32BIT)) {
 			gpa_t lo = lower_32_bits(vcpu->arch.sta.shmem);
 
-			vcpu->arch.sta.shmem = ((gpa_t)value << 32);
-			vcpu->arch.sta.shmem |= lo;
+			new_shmem = ((gpa_t)value << 32);
+			new_shmem |= lo;
 		} else if (value != 0) {
 			return -EINVAL;
 		}
@@ -211,6 +212,11 @@ static int kvm_sbi_ext_sta_set_reg(struct kvm_vcpu *vcpu, unsigned long reg_num,
 		return -ENOENT;
 	}
 
+	if (new_shmem != INVALID_GPA && !IS_ALIGNED(new_shmem, 64))
+		return -EINVAL;
+
+	vcpu->arch.sta.shmem = new_shmem;
+
 	return 0;
 }
 
-- 
2.34.1

[PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function

[Jiakai Xu]

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@oss.qualcomm.com>
Signed-off-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut@gmail.com>
---
V8 -> V9: Created a temporary VM with one vCPU in
           check_steal_time_uapi() instead of adding extra vCPUs to the
           main VM.
          Made check_steal_time_uapi() parameterless for all architectures.
V7 -> V8: Used ST_GPA_BASE directly instead of
           st_gva[]/sync_global_to_guest() in x86_64 and ARM64
           check_steal_time_uapi().
          Created a temporary vcpu in ARM64 check_steal_time_uapi() to
           avoid EEXIST when steal_time_init() later sets IPA for vcpu[0].
          Removed unnecessary comment in RISC-V check_steal_time_uapi().
---
 tools/testing/selftests/kvm/steal_time.c | 67 ++++++++++++++++++------
 1 file changed, 51 insertions(+), 16 deletions(-)

diff --git a/tools/testing/selftests/kvm/steal_time.c b/tools/testing/selftests/kvm/steal_time.c
index 8edc1fca345ba..75ad067f27260 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 +93,21 @@ 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_vm *vm;
+	struct kvm_vcpu *vcpu;
+	int ret;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	ret = _vcpu_set_msr(vcpu, MSR_KVM_STEAL_TIME,
+			    (ulong)ST_GPA_BASE | KVM_STEAL_RESERVED_MASK);
+	TEST_ASSERT(ret == 0, "Bad GPA didn't fail");
+
+	kvm_vm_free(vm);
+}
+
 #elif defined(__aarch64__)
 
 /* PV_TIME_ST must have 64-byte alignment */
@@ -170,7 +179,6 @@ 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 +186,12 @@ 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 +204,36 @@ 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_vm *vm;
+	struct kvm_vcpu *vcpu;
+	uint64_t st_ipa;
+	int ret;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	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_ipa = (ulong)ST_GPA_BASE | 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_GPA_BASE;
+	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");
+
+	kvm_vm_free(vm);
+}
+
 #elif defined(__riscv)
 
 /* SBI STA shmem must have 64-byte alignment */
@@ -301,6 +330,10 @@ static void steal_time_dump(struct kvm_vm *vm, uint32_t vcpu_idx)
 	pr_info("\n");
 }
 
+static void check_steal_time_uapi()
+{
+}
+
 #endif
 
 static void *do_steal_time(void *arg)
@@ -369,6 +402,8 @@ int main(int ac, char **av)
 	TEST_REQUIRE(is_steal_time_supported(vcpus[0]));
 	ksft_set_plan(NR_VCPUS);
 
+	check_steal_time_uapi();
+
 	/* Run test on each VCPU */
 	for (i = 0; i < NR_VCPUS; ++i) {
 		steal_time_init(vcpus[i], i);
-- 
2.34.1

Re: [PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function

[kernel test robot]

Hi Jiakai,

kernel test robot noticed the following build warnings:

[auto build test WARNING on v6.19]
[cannot apply to kvm/queue kvm/next linus/master kvm/linux-next v7.0-rc1 next-20260227]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Jiakai-Xu/RISC-V-KVM-Validate-SBI-STA-shmem-alignment-in-kvm_sbi_ext_sta_set_reg/20260228-085648
base:   v6.19
patch link:    https://lore.kernel.org/r/20260228005355.823048-3-xujiakai2025%40iscas.ac.cn
patch subject: [PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function
config: arm64-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260228/202602280523.Y5Q8Pdft-lkp@intel.com/config)
compiler: aarch64-linux-gnu-gcc (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260228/202602280523.Y5Q8Pdft-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602280523.Y5Q8Pdft-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> steal_time.c:207:13: warning: function declaration isn't a prototype [-Wstrict-prototypes]
     207 | static void check_steal_time_uapi()
         |             ^~~~~~~~~~~~~~~~~~~~~
   cc1: note: unrecognized command-line option '-Wno-gnu-variable-sized-type-not-at-end' may have been intended to silence earlier diagnostics

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Re: Re: [PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function

[Jiakai Xu]

Hi all,

I received a notification from the kernel test robot regarding my patch. It indicates that void check_steal_time_uapi() should be changed to void check_steal_time_uapi(void) to avoid a compiler warning.

I would like to wait for the reviewers’ feedback on this patch. If there are no issues aside from this warning, I will submit the final version addressing the compiler warning. If there are other suggestions, I will incorporate them accordingly.

Thanks,
Jiakai

"kernel test robot" <lkp@intel.com>写道：
> Hi Jiakai,
> 
> kernel test robot noticed the following build warnings:
> 
> [auto build test WARNING on v6.19]
> [cannot apply to kvm/queue kvm/next linus/master kvm/linux-next v7.0-rc1 next-20260227]
> [If your patch is applied to the wrong git tree, kindly drop us a note.
> And when submitting patch, we suggest to use '--base' as documented in
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Jiakai-Xu/RISC-V-KVM-Validate-SBI-STA-shmem-alignment-in-kvm_sbi_ext_sta_set_reg/20260228-085648
> base:   v6.19
> patch link:    https://lore.kernel.org/r/20260228005355.823048-3-xujiakai2025%40iscas.ac.cn
> patch subject: [PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function
> config: arm64-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260228/202602280523.Y5Q8Pdft-lkp@intel.com/config)
> compiler: aarch64-linux-gnu-gcc (Debian 14.2.0-19) 14.2.0
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260228/202602280523.Y5Q8Pdft-lkp@intel.com/reproduce)
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202602280523.Y5Q8Pdft-lkp@intel.com/
> 
> All warnings (new ones prefixed by >>):
> 
> >> steal_time.c:207:13: warning: function declaration isn't a prototype [-Wstrict-prototypes]
>      207 | static void check_steal_time_uapi()
>          |             ^~~~~~~~~~~~~~~~~~~~~
>    cc1: note: unrecognized command-line option '-Wno-gnu-variable-sized-type-not-at-end' may have been intended to silence earlier diagnostics
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://github.com/intel/lkp-tests/wiki

Re: [PATCH v9 2/3] KVM: selftests: Refactor UAPI tests into dedicated function

[Andrew Jones]

On Sat, Feb 28, 2026 at 12:53:54AM +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@oss.qualcomm.com>
> Signed-off-by: Jiakai Xu <xujiakai2025@iscas.ac.cn>
> Signed-off-by: Jiakai Xu <jiakaiPeanut@gmail.com>
> ---
> V8 -> V9: Created a temporary VM with one vCPU in
>            check_steal_time_uapi() instead of adding extra vCPUs to the
>            main VM.
>           Made check_steal_time_uapi() parameterless for all architectures.
> V7 -> V8: Used ST_GPA_BASE directly instead of
>            st_gva[]/sync_global_to_guest() in x86_64 and ARM64
>            check_steal_time_uapi().
>           Created a temporary vcpu in ARM64 check_steal_time_uapi() to
>            avoid EEXIST when steal_time_init() later sets IPA for vcpu[0].
>           Removed unnecessary comment in RISC-V check_steal_time_uapi().
> ---
>  tools/testing/selftests/kvm/steal_time.c | 67 ++++++++++++++++++------
>  1 file changed, 51 insertions(+), 16 deletions(-)

Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>

[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@iscas.ac.cn>
Signed-off-by: Jiakai Xu <jiakaiPeanut@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

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

[Andrew Jones]

On Sat, Feb 28, 2026 at 12:53:55AM +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 <xujiakai2025@iscas.ac.cn>
> Signed-off-by: Jiakai Xu <jiakaiPeanut@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(+)
>

Reviewed-by: Andrew Jones <andrew.jones@oss.qualcomm.com>