linux-kernel - [PATCH v9 28/30] KVM: arm64: selftests: Skip impossible invalid value tests

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Message-Id: <20251223-kvm-arm64-sme-v9-28-8be3867cb883@kernel.org>
Date: Tue, 23 Dec 2025 01:21:22 +0000
From: Mark Brown <broonie@...nel.org>
To: Marc Zyngier <maz@...nel.org>, Joey Gouly <joey.gouly@....com>, 
 Catalin Marinas <catalin.marinas@....com>, 
 Suzuki K Poulose <suzuki.poulose@....com>, Will Deacon <will@...nel.org>, 
 Paolo Bonzini <pbonzini@...hat.com>, Jonathan Corbet <corbet@....net>, 
 Shuah Khan <shuah@...nel.org>, Oliver Upton <oupton@...nel.org>
Cc: Dave Martin <Dave.Martin@....com>, Fuad Tabba <tabba@...gle.com>, 
 Mark Rutland <mark.rutland@....com>, Ben Horgan <ben.horgan@....com>, 
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
 linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org, 
 Peter Maydell <peter.maydell@...aro.org>, 
 Eric Auger <eric.auger@...hat.com>, Mark Brown <broonie@...nel.org>
Subject: [PATCH v9 28/30] KVM: arm64: selftests: Skip impossible invalid
 value tests

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@...nel.org>
---
 tools/testing/selftests/kvm/arm64/set_id_regs.c | 58 ++++++++++++++++++++-----
 1 file changed, 46 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/kvm/arm64/set_id_regs.c b/tools/testing/selftests/kvm/arm64/set_id_regs.c
index 322cd13b9352..641194c5005a 100644
--- a/tools/testing/selftests/kvm/arm64/set_id_regs.c
+++ b/tools/testing/selftests/kvm/arm64/set_id_regs.c
@@ -318,11 +318,12 @@ uint64_t get_safe_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 }
 
 /* Return an invalid value to a given ftr_bits an ftr value */
-uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
+uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr,
+			   bool *skip)
 {
 	uint64_t 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) {
@@ -330,42 +331,72 @@ uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 			ftr = max((uint64_t)ftr_bits->safe_val + 1, ftr + 1);
 			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((uint64_t)ftr_bits->safe_val + 1, ftr + 1);
+			if (ftr > ftr_max)
+				*skip = true;
 			break;
 		case FTR_LOWER_SAFE:
-			ftr++;
+			if (ftr == ftr_max)
+				*skip = true;
+			else
+				ftr++;
 			break;
 		case FTR_HIGHER_SAFE:
-			ftr--;
-			break;
-		case FTR_HIGHER_OR_ZERO_SAFE:
 			if (ftr == 0)
-				ftr = ftr_max - 1;
+				*skip = true;
 			else
 				ftr--;
 			break;
+		case FTR_HIGHER_OR_ZERO_SAFE:
+			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;
+		*skip = true;
 	}
 
 	return ftr;
@@ -400,12 +431,15 @@ static void test_reg_set_fail(struct kvm_vcpu *vcpu, uint64_t reg,
 	uint8_t shift = ftr_bits->shift;
 	uint64_t mask = ftr_bits->mask;
 	uint64_t 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