selftests: KVM: Provide descriptive assertions in kvm_binary_stats_test

As it turns out, tests sometimes fail. When that is the case, packing
the test assertion with as much relevant information helps track down
the problem more quickly.

Sharpen up the stat descriptor assertions in kvm_binary_stats_test to
more precisely describe the reason for the test assertion and which
stat is to blame.
Signed-off-by: NOliver Upton <oupton@google.com>
Reviewed-by: NAndrew Jones <andrew.jones@linux.dev>
Message-Id: <20220719143134.3246798-3-oliver.upton@linux.dev>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/kvm_binary_stats_test.c

@@ -31,6 +31,7 @@ static void stats_test(int stats_fd)
 	struct kvm_stats_desc *stats_desc;
 	u64 *stats_data;
 	struct kvm_stats_desc *pdesc;
+	u32 type, unit, base;
 
 	/* Read kvm stats header */
 	read_stats_header(stats_fd, &header);
@@ -72,18 +73,21 @@ static void stats_test(int stats_fd)
 	/* Sanity check for fields in descriptors */
 	for (i = 0; i < header.num_desc; ++i) {
 		pdesc = get_stats_descriptor(stats_desc, i, &header);
+		type = pdesc->flags & KVM_STATS_TYPE_MASK;
+		unit = pdesc->flags & KVM_STATS_UNIT_MASK;
+		base = pdesc->flags & KVM_STATS_BASE_MASK;
 
 		/* Check name string */
 		TEST_ASSERT(strlen(pdesc->name) < header.name_size,
 			    "KVM stats name (index: %d) too long", i);
 
 		/* Check type,unit,base boundaries */
-		TEST_ASSERT((pdesc->flags & KVM_STATS_TYPE_MASK) <= KVM_STATS_TYPE_MAX,
-			    "Unknown KVM stats type");
-		TEST_ASSERT((pdesc->flags & KVM_STATS_UNIT_MASK) <= KVM_STATS_UNIT_MAX,
-			    "Unknown KVM stats unit");
-		TEST_ASSERT((pdesc->flags & KVM_STATS_BASE_MASK) <= KVM_STATS_BASE_MAX,
-			    "Unknown KVM stats base");
+		TEST_ASSERT(type <= KVM_STATS_TYPE_MAX,
+			    "Unknown KVM stats (%s) type: %u", pdesc->name, type);
+		TEST_ASSERT(unit <= KVM_STATS_UNIT_MAX,
+			    "Unknown KVM stats (%s) unit: %u", pdesc->name, unit);
+		TEST_ASSERT(base <= KVM_STATS_BASE_MAX,
+			    "Unknown KVM stats (%s) base: %u", pdesc->name, base);
 
 		/*
 		 * Check exponent for stats unit
@@ -97,10 +101,14 @@ static void stats_test(int stats_fd)
 		case KVM_STATS_UNIT_NONE:
 		case KVM_STATS_UNIT_BYTES:
 		case KVM_STATS_UNIT_CYCLES:
-			TEST_ASSERT(pdesc->exponent >= 0, "Unsupported KVM stats unit");
+			TEST_ASSERT(pdesc->exponent >= 0,
+				    "Unsupported KVM stats (%s) exponent: %i",
+				    pdesc->name, pdesc->exponent);
 			break;
 		case KVM_STATS_UNIT_SECONDS:
-			TEST_ASSERT(pdesc->exponent <= 0, "Unsupported KVM stats unit");
+			TEST_ASSERT(pdesc->exponent <= 0,
+				    "Unsupported KVM stats (%s) exponent: %i",
+				    pdesc->name, pdesc->exponent);
 			break;
 		}