KVM: arm64: selftests: Handle feature fields with nonzero minimum value correctly

There are some feature fields with nonzero minimum valid value. Make
sure get_safe_value() won't return invalid field values for them.
Also fix a bug that wrongly uses the feature bits type as the feature
bits sign causing all fields as signed in the get_safe_value() and
get_invalid_value().

Fixes: 54a9ea73 ("KVM: arm64: selftests: Test for setting ID register from usersapce")
Reported-by: Zenghui Yu <yuzenghui@huawei.com>
Reported-by: Itaru Kitayama <itaru.kitayama@linux.dev>
Tested-by: Itaru Kitayama <itaru.kitayama@fujitsu.com>
Signed-off-by: Jing Zhang <jingzhangos@google.com>
Link: https://lore.kernel.org/r/20240115220210.3966064-2-jingzhangos@google.comSigned-off-by: Oliver Upton <oliver.upton@linux.dev>

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

@@ -32,6 +32,10 @@ struct reg_ftr_bits {
 	enum ftr_type type;
 	uint8_t shift;
 	uint64_t mask;
+	/*
+	 * For FTR_EXACT, safe_val is used as the exact safe value.
+	 * For FTR_LOWER_SAFE, safe_val is used as the minimal safe value.
+	 */
 	int64_t safe_val;
 };
 
@@ -65,13 +69,13 @@ struct test_feature_reg {
 
 static const struct reg_ftr_bits ftr_id_aa64dfr0_el1[] = {
 	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, PMUVer, 0),
-	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, DebugVer, 0),
+	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, DebugVer, ID_AA64DFR0_EL1_DebugVer_IMP),
 	REG_FTR_END,
 };
 
 static const struct reg_ftr_bits ftr_id_dfr0_el1[] = {
-	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_DFR0_EL1, PerfMon, 0),
-	REG_FTR_BITS(FTR_LOWER_SAFE, ID_DFR0_EL1, CopDbg, 0),
+	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_DFR0_EL1, PerfMon, ID_DFR0_EL1_PerfMon_PMUv3),
+	REG_FTR_BITS(FTR_LOWER_SAFE, ID_DFR0_EL1, CopDbg, ID_DFR0_EL1_CopDbg_Armv8),
 	REG_FTR_END,
 };
 
@@ -224,13 +228,13 @@ uint64_t get_safe_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 {
 	uint64_t ftr_max = GENMASK_ULL(ARM64_FEATURE_FIELD_BITS - 1, 0);
 
-	if (ftr_bits->type == FTR_UNSIGNED) {
+	if (ftr_bits->sign == FTR_UNSIGNED) {
 		switch (ftr_bits->type) {
 		case FTR_EXACT:
 			ftr = ftr_bits->safe_val;
 			break;
 		case FTR_LOWER_SAFE:
-			if (ftr > 0)
+			if (ftr > ftr_bits->safe_val)
 				ftr--;
 			break;
 		case FTR_HIGHER_SAFE:
@@ -252,7 +256,7 @@ uint64_t get_safe_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 			ftr = ftr_bits->safe_val;
 			break;
 		case FTR_LOWER_SAFE:
-			if (ftr > 0)
+			if (ftr > ftr_bits->safe_val)
 				ftr--;
 			break;
 		case FTR_HIGHER_SAFE:
@@ -276,7 +280,7 @@ uint64_t get_invalid_value(const struct reg_ftr_bits *ftr_bits, uint64_t ftr)
 {
 	uint64_t ftr_max = GENMASK_ULL(ARM64_FEATURE_FIELD_BITS - 1, 0);
 
-	if (ftr_bits->type == FTR_UNSIGNED) {
+	if (ftr_bits->sign == FTR_UNSIGNED) {
 		switch (ftr_bits->type) {
 		case FTR_EXACT:
 			ftr = max((uint64_t)ftr_bits->safe_val + 1, ftr + 1);