[PATCH v12 27/29] KVM: arm64: selftests: Skip impossible invalid value tests

[Mark Brown <broonie@kernel.org>]

The set_id_regs test currently assumes that there will always be invalid
values available in bitfields for it to generate but this may not be the
case if the architecture has defined meanings for every possible value for
the bitfield. An assert added in commit bf09ee918053e ("KVM: arm64:
selftests: Remove ARM64_FEATURE_FIELD_BITS and its last user") refuses to
run for single bit fields which will show the issue most readily but there
is no reason wider ones can't show the same issue.

Rework the tests for invalid value to check if an invalid value can be
generated and skip the test if not, removing the assert.

Signed-off-by: Mark Brown <broonie@kernel.org>
---
 tools/testing/selftests/kvm/arm64/set_id_regs.c | 64 +++++++++++++++++++++----
 1 file changed, 54 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/set_id_regs.c b/tools/testing/selftests/kvm/arm64/set_id_regs.c
index 9eceac84e297..da9349bf31ab 100644
--- a/tools/testing/selftests/kvm/arm64/set_id_regs.c
+++ b/tools/testing/selftests/kvm/arm64/set_id_regs.c
@@ -327,54 +327,95 @@ u64 get_safe_value(const struct reg_ftr_bits *ftr_bits, u64 ftr)
 }
 
 /* Return an invalid value to a given ftr_bits an ftr value */
-u64 get_invalid_value(const struct reg_ftr_bits *ftr_bits, u64 ftr)
+u64 get_invalid_value(const struct reg_ftr_bits *ftr_bits, u64 ftr, bool *skip)
 {
 	u64 ftr_max = ftr_bits->mask >> ftr_bits->shift;
 
-	TEST_ASSERT(ftr_max > 1, "This test doesn't support single bit features");
+	*skip = false;
 
 	if (ftr_bits->sign == FTR_UNSIGNED) {
 		switch (ftr_bits->type) {
 		case FTR_EXACT:
 			ftr = max((u64)ftr_bits->safe_val + 1, ftr + 1);
+			if (ftr >= ftr_max)
+				*skip = true;
 			break;
 		case FTR_LOWER_SAFE:
+			if (ftr == ftr_max)
+				*skip = true;
 			ftr++;
 			break;
 		case FTR_HIGHER_SAFE:
+			if (ftr == 0)
+				*skip = true;
 			ftr--;
 			break;
 		case FTR_HIGHER_OR_ZERO_SAFE:
-			if (ftr == 0)
+			switch (ftr) {
+			case 0:
 				ftr = ftr_max;
-			else
+				break;
+			case 1:
+				*skip = true;
+				break;
+			default:
 				ftr--;
+				break;
+			}
 			break;
 		default:
+			*skip = true;
 			break;
 		}
 	} else if (ftr != ftr_max) {
 		switch (ftr_bits->type) {
 		case FTR_EXACT:
 			ftr = max((u64)ftr_bits->safe_val + 1, ftr + 1);
+			if (ftr >= ftr_max)
+				*skip = true;
 			break;
 		case FTR_LOWER_SAFE:
 			ftr++;
 			break;
 		case FTR_HIGHER_SAFE:
-			ftr--;
+			/* FIXME: "need to check for the actual highest." */
+			if (ftr == 0 || ftr == ftr_max)
+				*skip = true;
+			else
+				ftr--;
 			break;
 		case FTR_HIGHER_OR_ZERO_SAFE:
-			if (ftr == 0)
-				ftr = ftr_max - 1;
-			else
+			switch (ftr) {
+			case 0:
+				if (ftr_max > 1)
+					ftr = ftr_max - 1;
+				else
+					*skip = true;
+				break;
+			case 1:
+				*skip = true;
+				break;
+			default:
 				ftr--;
+				break;
+			}
 			break;
 		default:
+			*skip = true;
 			break;
 		}
 	} else {
-		ftr = 0;
+		switch (ftr_bits->type) {
+		case FTR_LOWER_SAFE:
+			if (ftr == 0)
+				*skip = true;
+			else
+				ftr = 0;
+			break;
+		default:
+			*skip = true;
+			break;
+		}
 	}
 
 	return ftr;
@@ -409,12 +450,15 @@ static void test_reg_set_fail(struct kvm_vcpu *vcpu, u64 reg,
 	u8 shift = ftr_bits->shift;
 	u64 mask = ftr_bits->mask;
 	u64 val, old_val, ftr;
+	bool skip;
 	int r;
 
 	val = vcpu_get_reg(vcpu, reg);
 	ftr = (val & mask) >> shift;
 
-	ftr = get_invalid_value(ftr_bits, ftr);
+	ftr = get_invalid_value(ftr_bits, ftr, &skip);
+	if (skip)
+		return;
 
 	old_val = val;
 	ftr <<= shift;

-- 
2.47.3