[PATCH v1] KVM: arm64: selftests: Handle feature fields with nonzero minimum value correctly

[Suzuki K Poulose]

On 09/01/2024 16:56, Jing Zhang wrote:
> 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: 54a9ea73527d ("KVM: arm64: selftests: Test for setting ID register from usersapce")
> Reported-by: Zenghui Yu <yuzenghui at huawei.com>
> Reported-by: Itaru Kitayama <itaru.kitayama at linux.dev>
> Signed-off-by: Jing Zhang <jingzhangos at google.com>
> ---
>   .../selftests/kvm/aarch64/set_id_regs.c       | 20 +++++++++++++++----
>   1 file changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/aarch64/set_id_regs.c b/tools/testing/selftests/kvm/aarch64/set_id_regs.c
> index bac05210b539..f17454dc6d9e 100644
> --- a/tools/testing/selftests/kvm/aarch64/set_id_regs.c
> +++ b/tools/testing/selftests/kvm/aarch64/set_id_regs.c
> @@ -224,13 +224,20 @@ 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)
> +			uint64_t min_safe = 0;
> +
> +			if (!strcmp(ftr_bits->name, "ID_AA64DFR0_EL1_DebugVer"))
> +				min_safe = ID_AA64DFR0_EL1_DebugVer_IMP;
> +			else if (!strcmp(ftr_bits->name, "ID_DFR0_EL1_CopDbg"))
> +				min_safe = ID_DFR0_EL1_CopDbg_Armv8;

Instead of hardcoding the safe value here in the code, why not "fix" the 
safe value in the ftr_id table and use ftr_bits->safe_val for both the
above cases ?

> +
> +			if (ftr > min_safe)
>   				ftr--;
>   			break;
>   		case FTR_HIGHER_SAFE:
> @@ -252,7 +259,12 @@ 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)
> +			uint64_t min_safe = 0;
> +
> +			if (!strcmp(ftr_bits->name, "ID_DFR0_EL1_PerfMon"))
> +				min_safe = ID_DFR0_EL1_PerfMon_PMUv3;
> +
> +			if (ftr > min_safe)
>   				ftr--;

Also, here, don't we need to type case both "ftr" and min_safe to 
int64_t for signed features ?

Suzuki

>   			break;
>   		case FTR_HIGHER_SAFE:
> @@ -276,7 +288,7 @@ 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);
> 
> base-commit: 0dd3ee31125508cd67f7e7172247f05b7fd1753a