Messages in this thread | | | Date | Mon, 4 Jul 2022 15:56:46 +0200 | Subject | Re: [PATCH v11 3/3] KVM: s390: resetting the Topology-Change-Report | From | Pierre Morel <> |
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On 7/4/22 11:35, Janis Schoetterl-Glausch wrote: > On 7/1/22 18:25, Pierre Morel wrote: >> During a subsystem reset the Topology-Change-Report is cleared. >> >> Let's give userland the possibility to clear the MTCR in the case >> of a subsystem reset. >> >> To migrate the MTCR, we give userland the possibility to >> query the MTCR state. >> >> We indicate KVM support for the CPU topology facility with a new >> KVM capability: KVM_CAP_S390_CPU_TOPOLOGY. >> >> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >> --- >> Documentation/virt/kvm/api.rst | 25 +++++++++++++++ >> arch/s390/include/uapi/asm/kvm.h | 10 ++++++ >> arch/s390/kvm/kvm-s390.c | 53 ++++++++++++++++++++++++++++++++ >> include/uapi/linux/kvm.h | 1 + >> 4 files changed, 89 insertions(+) >> >> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst >> index 11e00a46c610..5e086125d8ad 100644 >> --- a/Documentation/virt/kvm/api.rst >> +++ b/Documentation/virt/kvm/api.rst >> @@ -7956,6 +7956,31 @@ should adjust CPUID leaf 0xA to reflect that the PMU is disabled. >> When enabled, KVM will exit to userspace with KVM_EXIT_SYSTEM_EVENT of >> type KVM_SYSTEM_EVENT_SUSPEND to process the guest suspend request. >> >> +8.37 KVM_CAP_S390_CPU_TOPOLOGY >> +------------------------------ >> + >> +:Capability: KVM_CAP_S390_CPU_TOPOLOGY >> +:Architectures: s390 >> +:Type: vm >> + >> +This capability indicates that KVM will provide the S390 CPU Topology >> +facility which consist of the interpretation of the PTF instruction for >> +the function code 2 along with interception and forwarding of both the >> +PTF instruction with function codes 0 or 1 and the STSI(15,1,x) >> +instruction to the userland hypervisor. > The latter only if the user STSI capability is also enabled.
Hum, not sure about this. we can not set facility 11 and return 3 to STSI(15) for valid selectors.
I think that it was right before, KVM_CAP_S390_CPU_TOPOLOGY and KVM_CAP_S390_USER_STSI are independent in KVM, userland can turn on one and not the other. But KVM proposes both.
Of course it is stupid to turn on only KVM_CAP_S390_CPU_TOPOLOGY but KVM is not responsible for this userland is.
Otherwise, we need to check on KVM_CAP_S390_USER_STSI before authorizing KVM_CAP_S390_CPU_TOPOLOGY and that looks even more complicated for me, or we suppress the KVM_CAP_S390_CPU_TOPOLOGY and implement the all stsi(15) in the kernel what I really do not think is good because of the complexity of the userland API
>> + >> +The stfle facility 11, CPU Topology facility, should not be indicated >> +to the guest without this capability. >> + >> +When this capability is present, KVM provides a new attribute group >> +on vm fd, KVM_S390_VM_CPU_TOPOLOGY. >> +This new attribute allows to get, set or clear the Modified Change >> +Topology Report (MTCR) bit of the SCA through the kvm_device_attr >> +structure. >> + >> +When getting the Modified Change Topology Report value, the attr->addr >> +must point to a byte where the value will be stored. >> + >> 9. Known KVM API problems >> ========================= >> >> diff --git a/arch/s390/include/uapi/asm/kvm.h b/arch/s390/include/uapi/asm/kvm.h >> index 7a6b14874d65..df5e8279ffd0 100644 >> --- a/arch/s390/include/uapi/asm/kvm.h >> +++ b/arch/s390/include/uapi/asm/kvm.h >> @@ -74,6 +74,7 @@ struct kvm_s390_io_adapter_req { >> #define KVM_S390_VM_CRYPTO 2 >> #define KVM_S390_VM_CPU_MODEL 3 >> #define KVM_S390_VM_MIGRATION 4 >> +#define KVM_S390_VM_CPU_TOPOLOGY 5 >> >> /* kvm attributes for mem_ctrl */ >> #define KVM_S390_VM_MEM_ENABLE_CMMA 0 >> @@ -171,6 +172,15 @@ struct kvm_s390_vm_cpu_subfunc { >> #define KVM_S390_VM_MIGRATION_START 1 >> #define KVM_S390_VM_MIGRATION_STATUS 2 >> >> +/* kvm attributes for cpu topology */ >> +#define KVM_S390_VM_CPU_TOPO_MTCR_CLEAR 0 >> +#define KVM_S390_VM_CPU_TOPO_MTCR_SET 1 >> + >> +struct kvm_cpu_topology { >> + __u16 mtcr : 1; >> + __u16 reserved : 15; >> +}; > > This is no longer used, is it?
No, I sent the wrong patch it seems!! Sorry for that. There is nothing more in kvm.h now but the definition for KVM_S390_VM_CPU_TOPOLOGY
>> + >> /* for KVM_GET_REGS and KVM_SET_REGS */ >> struct kvm_regs { >> /* general purpose regs for s390 */ >> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >> index ee59b03f2e45..5029fe40adbd 100644 >> --- a/arch/s390/kvm/kvm-s390.c >> +++ b/arch/s390/kvm/kvm-s390.c >> @@ -606,6 +606,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> case KVM_CAP_S390_PROTECTED: >> r = is_prot_virt_host(); >> break; >> + case KVM_CAP_S390_CPU_TOPOLOGY: >> + r = test_facility(11); >> + break; >> default: >> r = 0; >> } >> @@ -817,6 +820,20 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) >> icpt_operexc_on_all_vcpus(kvm); >> r = 0; >> break; >> + case KVM_CAP_S390_CPU_TOPOLOGY: >> + r = -EINVAL; >> + mutex_lock(&kvm->lock); >> + if (kvm->created_vcpus) { >> + r = -EBUSY; >> + } else if (test_facility(11)) { >> + set_kvm_facility(kvm->arch.model.fac_mask, 11); >> + set_kvm_facility(kvm->arch.model.fac_list, 11); >> + r = 0; >> + } >> + mutex_unlock(&kvm->lock); >> + VM_EVENT(kvm, 3, "ENABLE: CPU TOPOLOGY %s", > > I still would go for consistency here, "ENABLE: CAP_S390_CPU_TOPOLOGY %s".
Yes, done.
> >> + r ? "(not available)" : "(success)"); >> + break; >> default: >> r = -EINVAL; >> break; >> @@ -1716,6 +1733,33 @@ static void kvm_s390_update_topology_change_report(struct kvm *kvm, bool val) >> read_unlock(&kvm->arch.sca_lock); >> } >> >> +static int kvm_s390_set_topology(struct kvm *kvm, struct kvm_device_attr *attr) >> +{ >> + if (!test_kvm_facility(kvm, 11)) >> + return -ENXIO; >> + >> + kvm_s390_update_topology_change_report(kvm, !!attr->attr); > > Will this not be automatically clamped to 0,1 if the argument has type bool?
I do not know, anyway done like this is sure.
>> + return 0; >> +} >> + >> +static int kvm_s390_get_topology(struct kvm *kvm, struct kvm_device_attr *attr) >> +{ >> + union sca_utility utility; >> + struct bsca_block *sca = kvm->arch.sca; >> + __u8 topo; >> + >> + if (!test_kvm_facility(kvm, 11)) >> + return -ENXIO; >> + > read_lock(&kvm->arch.sca_lock); > utility.val = READ_ONCE(kvm->arch.sca->utility.val); > read_unlock(&kvm->arch.sca_lock); > > And then get rid of the sca declaration.
OK
>> + topo = utility.mtcr; >> + >> + if (copy_to_user((void __user *)attr->addr, &topo, sizeof(topo))) >> + return -EFAULT; >> + >> + return 0; >> +} >> + > [...] >
-- Pierre Morel IBM Lab Boeblingen
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