KVM: selftests: arm64: Store expected register value in set_id_regs

Rather than comparing against what is returned by the ioctl, store
expected values for the feature ID registers in a table and compare with
that instead.

This will prove useful for subsequent tests involving vCPU reset.
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240502233529.1958459-6-oliver.upton@linux.devSigned-off-by: Marc Zyngier <maz@kernel.org>

tools/testing/selftests/kvm/aarch64/set_id_regs.c

@@ -327,7 +327,7 @@ uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 	return ftr;
 }
 
-static void test_reg_set_success(struct kvm_vcpu *vcpu, uint64_t reg,
+static uint64_t test_reg_set_success(struct kvm_vcpu *vcpu, uint64_t reg,
 				     const struct reg_ftr_bits *ftr_bits)
 {
 	uint8_t shift = ftr_bits->shift;
@@ -346,6 +346,8 @@ static void test_reg_set_success(struct kvm_vcpu *vcpu, uint64_t reg,
 	vcpu_set_reg(vcpu, reg, val);
 	vcpu_get_reg(vcpu, reg, &new_val);
 	TEST_ASSERT_EQ(new_val, val);
+
+	return new_val;
 }
 
 static void test_reg_set_fail(struct kvm_vcpu *vcpu, uint64_t reg,
@@ -374,6 +376,14 @@ static void test_reg_set_fail(struct kvm_vcpu *vcpu, uint64_t reg,
 	TEST_ASSERT_EQ(val, old_val);
 }
 
+static uint64_t test_reg_vals[KVM_ARM_FEATURE_ID_RANGE_SIZE];
+
+#define encoding_to_range_idx(encoding)							\
+	KVM_ARM_FEATURE_ID_RANGE_IDX(sys_reg_Op0(encoding), sys_reg_Op1(encoding),	\
+				     sys_reg_CRn(encoding), sys_reg_CRm(encoding),	\
+				     sys_reg_Op2(encoding))
+
+
 static void test_vm_ftr_id_regs(struct kvm_vcpu *vcpu, bool aarch64_only)
 {
 	uint64_t masks[KVM_ARM_FEATURE_ID_RANGE_SIZE];
@@ -398,9 +408,7 @@ static void test_vm_ftr_id_regs(struct kvm_vcpu *vcpu, bool aarch64_only)
 		int idx;
 
 		/* Get the index to masks array for the idreg */
-		idx = KVM_ARM_FEATURE_ID_RANGE_IDX(sys_reg_Op0(reg_id), sys_reg_Op1(reg_id),
-						   sys_reg_CRn(reg_id), sys_reg_CRm(reg_id),
-						   sys_reg_Op2(reg_id));
+		idx = encoding_to_range_idx(reg_id);
 
 		for (int j = 0;  ftr_bits[j].type != FTR_END; j++) {
 			/* Skip aarch32 reg on aarch64 only system, since they are RAZ/WI. */
@@ -414,7 +422,9 @@ static void test_vm_ftr_id_regs(struct kvm_vcpu *vcpu, bool aarch64_only)
 			TEST_ASSERT_EQ(masks[idx] & ftr_bits[j].mask, ftr_bits[j].mask);
 
 			test_reg_set_fail(vcpu, reg, &ftr_bits[j]);
-			test_reg_set_success(vcpu, reg, &ftr_bits[j]);
+
+			test_reg_vals[idx] = test_reg_set_success(vcpu, reg,
+								  &ftr_bits[j]);
 
 			ksft_test_result_pass("%s\n", ftr_bits[j].name);
 		}
@@ -425,7 +435,6 @@ static void test_guest_reg_read(struct kvm_vcpu *vcpu)
 {
 	bool done = false;
 	struct ucall uc;
-	uint64_t val;
 
 	while (!done) {
 		vcpu_run(vcpu);
@@ -436,8 +445,8 @@ static void test_guest_reg_read(struct kvm_vcpu *vcpu)
 			break;
 		case UCALL_SYNC:
 			/* Make sure the written values are seen by guest */
-			vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(uc.args[2]), &val);
-			TEST_ASSERT_EQ(val, uc.args[3]);
+			TEST_ASSERT_EQ(test_reg_vals[encoding_to_range_idx(uc.args[2])],
+				       uc.args[3]);
 			break;
 		case UCALL_DONE:
 			done = true;