On Fri, 3 Nov 2023 18:30:08 +0100
Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx> wrote:
> Directly use the size of the arrays instead of going through the
> indirection of kvm_s390_fac_size().
> Don't use magic number for the number of entries in the non hypervisor
> managed facility bit mask list.
> Make the constraint of that number on kvm_s390_fac_base obvious.
> Get rid of implicit double anding of stfle_fac_list.
>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@xxxxxxxxxxxxx>
> ---
>
>
> I found it confusing before and think it's nicer this way but
> it might be needless churn.
some things are probably overkill
>
>
> arch/s390/kvm/kvm-s390.c | 44 +++++++++++++++++-----------------------
> 1 file changed, 19 insertions(+), 25 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index b3f17e014cab..e00ab2f38c89 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -217,33 +217,25 @@ static int async_destroy = 1;
> module_param(async_destroy, int, 0444);
> MODULE_PARM_DESC(async_destroy, "Asynchronous destroy for protected guests");
>
> -/*
> - * For now we handle at most 16 double words as this is what the s390 base
> - * kernel handles and stores in the prefix page. If we ever need to go beyond
> - * this, this requires changes to code, but the external uapi can stay.
> - */
> -#define SIZE_INTERNAL 16
> -
> +#define HMFAI_DWORDS 16
> /*
> * Base feature mask that defines default mask for facilities. Consists of the
> * defines in FACILITIES_KVM and the non-hypervisor managed bits.
> */
> -static unsigned long kvm_s390_fac_base[SIZE_INTERNAL] = { FACILITIES_KVM };
> +static unsigned long kvm_s390_fac_base[HMFAI_DWORDS] = { FACILITIES_KVM };
> +static_assert(ARRAY_SIZE(((long[]){ FACILITIES_KVM })) <= HMFAI_DWORDS);
> +static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_MASK_SIZE_U64);
> +static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= S390_ARCH_FAC_LIST_SIZE_U64);
> +static_assert(ARRAY_SIZE(kvm_s390_fac_base) <= ARRAY_SIZE(stfle_fac_list));
> +
> /*
> * Extended feature mask. Consists of the defines in FACILITIES_KVM_CPUMODEL
> * and defines the facilities that can be enabled via a cpu model.
> */
> -static unsigned long kvm_s390_fac_ext[SIZE_INTERNAL] = { FACILITIES_KVM_CPUMODEL };
> -
> -static unsigned long kvm_s390_fac_size(void)
> -{
> - BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_MASK_SIZE_U64);
> - BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_LIST_SIZE_U64);
> - BUILD_BUG_ON(SIZE_INTERNAL * sizeof(unsigned long) >
> - sizeof(stfle_fac_list));
> -
> - return SIZE_INTERNAL;
> -}
> +static const unsigned long kvm_s390_fac_ext[] = { FACILITIES_KVM_CPUMODEL };
this was sized to [SIZE_INTERNAL], now it doesn't have a fixed size. is
this intentional?
> +static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_MASK_SIZE_U64);
> +static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= S390_ARCH_FAC_LIST_SIZE_U64);
> +static_assert(ARRAY_SIZE(kvm_s390_fac_ext) <= ARRAY_SIZE(stfle_fac_list));
>
> /* available cpu features supported by kvm */
> static DECLARE_BITMAP(kvm_s390_available_cpu_feat, KVM_S390_VM_CPU_FEAT_NR_BITS);
> @@ -3341,13 +3333,16 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> kvm->arch.sie_page2->kvm = kvm;
> kvm->arch.model.fac_list = kvm->arch.sie_page2->fac_list;
>
> - for (i = 0; i < kvm_s390_fac_size(); i++) {
> + for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_base); i++) {
> kvm->arch.model.fac_mask[i] = stfle_fac_list[i] &
> - (kvm_s390_fac_base[i] |
> - kvm_s390_fac_ext[i]);
> + kvm_s390_fac_base[i];
> kvm->arch.model.fac_list[i] = stfle_fac_list[i] &
> kvm_s390_fac_base[i];
> }
> + for (i = 0; i < ARRAY_SIZE(kvm_s390_fac_ext); i++) {
> + kvm->arch.model.fac_mask[i] |= stfle_fac_list[i] &
> + kvm_s390_fac_ext[i];
> + }
I like it better when it's all in one place, instead of having two loops
> kvm->arch.model.subfuncs = kvm_s390_available_subfunc;
>
> /* we are always in czam mode - even on pre z14 machines */
> @@ -5859,9 +5854,8 @@ static int __init kvm_s390_init(void)
> return -EINVAL;
> }
>
> - for (i = 0; i < 16; i++)
> - kvm_s390_fac_base[i] |=
> - stfle_fac_list[i] & nonhyp_mask(i);
> + for (i = 0; i < HMFAI_DWORDS; i++)
> + kvm_s390_fac_base[i] |= nonhyp_mask(i);
where did the stfle_fac_list[i] go?
>
> r = __kvm_s390_init();
> if (r)
