linux-kernel - [PATCH v2 4/4] KVM: selftests: arm64: Skip all 32 bit IDs when set_id

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Message-Id: <20251114-kvm-arm64-set-id-regs-aarch64-v2-4-672f214f41bf@kernel.org>
Date: Fri, 14 Nov 2025 15:35:37 +0000
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
 Paolo Bonzini <pbonzini@...hat.com>, Shuah Khan <shuah@...nel.org>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 kvm@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: [PATCH v2 4/4] KVM: selftests: arm64: Skip all 32 bit IDs when
 set_id_regs is aarch64 only

On an aarch64 only system the 32 bit ID registers have UNDEFINED values.
As a result set_id_regs skips tests for setting fields in these registers
when testing an aarch64 only guest. This has the side effect of meaning
that we don't record an expected value for these registers, meaning that
when the subsequent tests for values being visible in guests and preserved
over reset check the value they can spuriously fail. This can be seen by
running on an emulated system with both NV and 32 bit enabled, NV will
result in the guests created by the test program being 64 bit only but
the 32 bit ID registers will have values.

Also skip those tests that use the values set in the field setting tests
for aarch64 only guests in order to avoid these spurious failures.

Signed-off-by: Mark Brown <broonie@...nel.org>
---
 tools/testing/selftests/kvm/arm64/set_id_regs.c | 42 +++++++++++++++++--------
 1 file changed, 29 insertions(+), 13 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/set_id_regs.c b/tools/testing/selftests/kvm/arm64/set_id_regs.c
index abe97f9293c9..55e13aa758ff 100644
--- a/tools/testing/selftests/kvm/arm64/set_id_regs.c
+++ b/tools/testing/selftests/kvm/arm64/set_id_regs.c
@@ -671,7 +671,7 @@ static void test_user_set_mte_reg(struct kvm_vcpu *vcpu)
 		ksft_test_result_pass("ID_AA64PFR1_EL1.MTE_frac no longer 0xF\n");
 }
 
-static void test_guest_reg_read(struct kvm_vcpu *vcpu)
+static void test_guest_reg_read(struct kvm_vcpu *vcpu, bool aarch64_only)
 {
 	bool done = false;
 	struct ucall uc;
@@ -690,6 +690,13 @@ static void test_guest_reg_read(struct kvm_vcpu *vcpu)
 			reg_id = uc.args[2];
 			guest_val = uc.args[3];
 			expected_val = test_reg_vals[encoding_to_range_idx(reg_id)];
+
+			if (aarch64_only && sys_reg_CRm(reg_id) < 4) {
+				ksft_test_result_skip("%s value seen in guest\n",
+						      get_reg_name(reg_id));
+				break;
+			}
+
 			match = expected_val == guest_val;
 			if (!match)
 				ksft_print_msg("%lx != %lx\n",
@@ -781,12 +788,19 @@ static void test_vcpu_non_ftr_id_regs(struct kvm_vcpu *vcpu)
 	ksft_test_result_pass("%s\n", __func__);
 }
 
-static void test_assert_id_reg_unchanged(struct kvm_vcpu *vcpu, uint32_t encoding)
+static void test_assert_id_reg_unchanged(struct kvm_vcpu *vcpu, uint32_t encoding,
+					 bool aarch64_only)
 {
 	size_t idx = encoding_to_range_idx(encoding);
 	uint64_t observed;
 	bool pass;
 
+	if (aarch64_only && sys_reg_CRm(encoding) < 4) {
+		ksft_test_result_skip("%s unchanged by reset\n",
+				      get_reg_name(encoding));
+		return;
+	}
+
 	observed = vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(encoding));
 	pass = test_reg_vals[idx] == observed;
 	if (!pass)
@@ -797,7 +811,8 @@ static void test_assert_id_reg_unchanged(struct kvm_vcpu *vcpu, uint32_t encodin
 
 #define ID_REG_RESET_UNCHANGED_TEST (ARRAY_SIZE(test_regs) + 6)
 
-static void test_reset_preserves_id_regs(struct kvm_vcpu *vcpu)
+static void test_reset_preserves_id_regs(struct kvm_vcpu *vcpu,
+					 bool aarch64_only)
 {
 	/*
 	 * Calls KVM_ARM_VCPU_INIT behind the scenes, which will do an
@@ -806,14 +821,15 @@ static void test_reset_preserves_id_regs(struct kvm_vcpu *vcpu)
 	aarch64_vcpu_setup(vcpu, NULL);
 
 	for (int i = 0; i < ARRAY_SIZE(test_regs); i++)
-		test_assert_id_reg_unchanged(vcpu, test_regs[i].reg);
-
-	test_assert_id_reg_unchanged(vcpu, SYS_MPIDR_EL1);
-	test_assert_id_reg_unchanged(vcpu, SYS_CLIDR_EL1);
-	test_assert_id_reg_unchanged(vcpu, SYS_CTR_EL0);
-	test_assert_id_reg_unchanged(vcpu, SYS_MIDR_EL1);
-	test_assert_id_reg_unchanged(vcpu, SYS_REVIDR_EL1);
-	test_assert_id_reg_unchanged(vcpu, SYS_AIDR_EL1);
+		test_assert_id_reg_unchanged(vcpu, test_regs[i].reg,
+					     aarch64_only);
+
+	test_assert_id_reg_unchanged(vcpu, SYS_MPIDR_EL1, aarch64_only);
+	test_assert_id_reg_unchanged(vcpu, SYS_CLIDR_EL1, aarch64_only);
+	test_assert_id_reg_unchanged(vcpu, SYS_CTR_EL0, aarch64_only);
+	test_assert_id_reg_unchanged(vcpu, SYS_MIDR_EL1, aarch64_only);
+	test_assert_id_reg_unchanged(vcpu, SYS_REVIDR_EL1, aarch64_only);
+	test_assert_id_reg_unchanged(vcpu, SYS_AIDR_EL1, aarch64_only);
 }
 
 int main(void)
@@ -855,9 +871,9 @@ int main(void)
 	test_user_set_mpam_reg(vcpu);
 	test_user_set_mte_reg(vcpu);
 
-	test_guest_reg_read(vcpu);
+	test_guest_reg_read(vcpu, aarch64_only);
 
-	test_reset_preserves_id_regs(vcpu);
+	test_reset_preserves_id_regs(vcpu, aarch64_only);
 
 	kvm_vm_free(vm);
 

-- 
2.47.2