On 19.02.2018 09:53, Christian Borntraeger wrote:
> Some facilities should only provided to the guest, if these are
> enabled by a CPU model. This allows to avoid capabilities and
> simply fallback to the cpumodel for deciding about a facility
> without enabling it for older QEMUs or QEMUs without a CPU
> model.
>
> Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> ---
> arch/s390/kvm/kvm-s390.c | 40 ++++++++++++++++++++++++++++++++--------
> arch/s390/kvm/kvm-s390.h | 2 --
> arch/s390/tools/gen_facilities.c | 20 ++++++++++++++++++++
> 3 files changed, 52 insertions(+), 10 deletions(-)
>
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 5b7fe80cda56..7d982690b1fc 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -151,13 +151,27 @@ static int nested;
> module_param(nested, int, S_IRUGO);
> MODULE_PARM_DESC(nested, "Nested virtualization support");
>
> -/* upper facilities limit for kvm */
> -unsigned long kvm_s390_fac_list_mask[16] = { FACILITIES_KVM };
>
> -unsigned long kvm_s390_fac_list_mask_size(void)
> +/*
> + * For now we handle not more than 16 double words as this is what
> + * the s390 base kernel handles and stores in 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
> +
> +/* upper facilities limit for kvm */
> +static unsigned long kvm_s390_fac_list_mask[SIZE_INTERNAL] = { FACILITIES_KVM };
> +/*
> + * facility bits that are in the mask, but initially not in the list.
> + * Those can be activated by the CPU model
> + */
> +static unsigned long kvm_s390_fac_model[SIZE_INTERNAL] = { FACILITIES_KVM_CPUMODEL };
_list_mask vs _model
Can we make this more consistent?
> +
> +static unsigned long kvm_s390_fac_size(void)
> {
> - BUILD_BUG_ON(ARRAY_SIZE(kvm_s390_fac_list_mask) > S390_ARCH_FAC_MASK_SIZE_U64);
> - return ARRAY_SIZE(kvm_s390_fac_list_mask);
> + BUILD_BUG_ON(SIZE_INTERNAL > S390_ARCH_FAC_MASK_SIZE_U64);
> + return SIZE_INTERNAL;
> }
>
> /* available cpu features supported by kvm */
> @@ -1946,17 +1960,27 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> memcpy(kvm->arch.model.fac_mask, S390_lowcore.stfle_fac_list,
> sizeof(S390_lowcore.stfle_fac_list));
> for (i = 0; i < S390_ARCH_FAC_LIST_SIZE_U64; i++) {
> - if (i < kvm_s390_fac_list_mask_size())
> - kvm->arch.model.fac_mask[i] &= kvm_s390_fac_list_mask[i];
> + if (i < kvm_s390_fac_size())
> + kvm->arch.model.fac_mask[i] &= (kvm_s390_fac_list_mask[i] |
> + kvm_s390_fac_model[i]);
> else
> kvm->arch.model.fac_mask[i] = 0UL;
> }
>
> - /* Populate the facility list initially. */
> + /* Populate the facility list initially as a copy of the mask */
> kvm->arch.model.fac_list = kvm->arch.sie_page2->fac_list;
> memcpy(kvm->arch.model.fac_list, kvm->arch.model.fac_mask,
> S390_ARCH_FAC_LIST_SIZE_BYTE);
>
If you need a loop either way, why not simply drop the memcpy and
instead do it explicitly in a single loop?
> + /*
> + * Disable facilities in the list that need CPU model support.
> + * Those are now in the mask but not in the list. Userspace can
> + * re-enable those that are in the mask via the CPU model
> + */
> + for (i = 0; i < S390_ARCH_FAC_LIST_SIZE_U64; i++)
> + if (i < kvm_s390_fac_size())
> + kvm->arch.model.fac_list[i] &= ~kvm_s390_fac_model[i];
> +
> /* we are always in czam mode - even on pre z14 machines */
> set_kvm_facility(kvm->arch.model.fac_mask, 138);
> set_kvm_facility(kvm->arch.model.fac_list, 138);
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 3c0a975c2477..75efb6835acc 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -295,8 +295,6 @@ void exit_sie(struct kvm_vcpu *vcpu);
> void kvm_s390_sync_request(int req, struct kvm_vcpu *vcpu);
> int kvm_s390_vcpu_setup_cmma(struct kvm_vcpu *vcpu);
> void kvm_s390_vcpu_unsetup_cmma(struct kvm_vcpu *vcpu);
> -unsigned long kvm_s390_fac_list_mask_size(void);
> -extern unsigned long kvm_s390_fac_list_mask[];
> void kvm_s390_set_cpu_timer(struct kvm_vcpu *vcpu, __u64 cputm);
> __u64 kvm_s390_get_cpu_timer(struct kvm_vcpu *vcpu);
>
> diff --git a/arch/s390/tools/gen_facilities.c b/arch/s390/tools/gen_facilities.c
> index 424a1ba4f874..37a77a3f280c 100644
> --- a/arch/s390/tools/gen_facilities.c
> +++ b/arch/s390/tools/gen_facilities.c
> @@ -62,6 +62,13 @@ static struct facility_def facility_defs[] = {
> }
> },
> {
> + /*
> + * FACILITIES_KVM contains the list of facilities that are
> + * part of the default facility mask and list passed to the
> + * initial CPU model. If no CPU model is used this, together
> + * with the non-hypervisor managed bits, is the maximum list
> + * of guest facilities supported by KVM.
> + */
> .name = "FACILITIES_KVM",
> .bits = (int[]){
> 0, /* N3 instructions */
> @@ -89,6 +96,19 @@ static struct facility_def facility_defs[] = {
> -1 /* END */
> }
> },
> + {
> + /*
> + * FACILITIES_KVM_CPUMODEL contains the list of facilities
> + * that can be enabled by CPU model code if the host supports
> + * it. These facilities are not passed to the guest without
> + * CPU model support.
> + */
> +
> + .name = "FACILITIES_KVM_CPUMODEL",
> + .bits = (int[]){
> + -1 /* END */
> + }
> + },
> };
>
> static void print_facility_list(struct facility_def *def)
>
General idea sounds sane.
If old user space already uses CPU models, it will only enable a sane
subset - as they are filtered.
New user space can enable new CPU models.
If user space doesn't use CPU models, only a sane subset will be enabled.
--
Thanks,
David / dhildenb
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