Messages in this thread | | | Date | Mon, 21 Feb 2022 09:10:29 +0100 | Subject | Re: [PATCH v7 1/1] s390x: KVM: guest support for topology function | From | Janosch Frank <> |
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On 2/18/22 19:24, Pierre Morel wrote: > > > On 2/18/22 18:27, Pierre Morel wrote: >> >> >> On 2/18/22 15:28, Janosch Frank wrote: >>> On 2/18/22 14:13, Pierre Morel wrote: >>>> >>>> >>>> On 2/17/22 18:17, Nico Boehr wrote: >>>>> On Thu, 2022-02-17 at 10:59 +0100, Pierre Morel wrote: >>>>> [...] >>>>>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c >>>>>> index 2296b1ff1e02..af7ea8488fa2 100644 >>>>>> --- a/arch/s390/kvm/kvm-s390.c >>>>>> +++ b/arch/s390/kvm/kvm-s390.c >>>>> [...] >>> >>> Why is there no interface to clear the SCA_UTILITY_MTCR on a subsystem >>> reset? >> >> Right, I had one in my first version based on interception but I forgot >> to implement an equivalent for KVM as I modified the implementation for >> interpretation. >> I will add this. >> >>> >>> >>>>>> -void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) >>>>>> +/** >>>>>> + * kvm_s390_vcpu_set_mtcr >>>>>> + * @vcp: the virtual CPU >>>>>> + * >>>>>> + * Is only relevant if the topology facility is present. >>>>>> + * >>>>>> + * Updates the Multiprocessor Topology-Change-Report to signal >>>>>> + * the guest with a topology change. >>>>>> + */ >>>>>> +static void kvm_s390_vcpu_set_mtcr(struct kvm_vcpu *vcpu) >>>>>> { >>>>>> + struct esca_block *esca = vcpu->kvm->arch.sca; >>>>> >>>>> utility is at the same offset for the bsca and the esca, still >>>>> wondering whether it is a good idea to assume esca here... >>>> >>>> We can take bsca to be coherent with the include file where we define >>>> ESCA_UTILITY_MTCR inside the bsca. >>>> And we can rename the define to SCA_UTILITY_MTCR as it is common for >>>> both BSCA and ESCA the (E) is too much. >>> >>> Yes and maybe add a comment that it's at the same offset for esca so >>> there won't come up further questions in the future. >> >> OK >> >>> >>>> >>>>> >>>>> [...] >>>>>> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h >>>>>> index 098831e815e6..af04ffbfd587 100644 >>>>>> --- a/arch/s390/kvm/kvm-s390.h >>>>>> +++ b/arch/s390/kvm/kvm-s390.h >>>>>> @@ -503,4 +503,29 @@ void kvm_s390_vcpu_crypto_reset_all(struct kvm >>>>>> *kvm); >>>>>> */ >>>>>> extern unsigned int diag9c_forwarding_hz; >>>>>> +#define S390_KVM_TOPOLOGY_NEW_CPU -1 >>>>>> +/** >>>>>> + * kvm_s390_topology_changed >>>>>> + * @vcpu: the virtual CPU >>>>>> + * >>>>>> + * If the topology facility is present, checks if the CPU toplogy >>>>>> + * viewed by the guest changed due to load balancing or CPU hotplug. >>>>>> + */ >>>>>> +static inline bool kvm_s390_topology_changed(struct kvm_vcpu *vcpu) >>>>>> +{ >>>>>> + if (!test_kvm_facility(vcpu->kvm, 11)) >>>>>> + return false; >>>>>> + >>>>>> + /* A new vCPU has been hotplugged */ >>>>>> + if (vcpu->arch.prev_cpu == S390_KVM_TOPOLOGY_NEW_CPU) >>>>>> + return true; >>>>>> + >>>>>> + /* The real CPU backing up the vCPU moved to another socket >>>>>> */ >>>>>> + if (topology_physical_package_id(vcpu->cpu) != >>>>>> + topology_physical_package_id(vcpu->arch.prev_cpu)) >>>>>> + return true; >>>>> >>>>> Why is it OK to look just at the physical package ID here? What if the >>>>> vcpu for example moves to a different book, which has a core with the >>>>> same physical package ID? >>> >>> I'll need to look up stsi 15* output to understand this. >>> But the architecture states that any change to the stsi 15 output sets >>> the change bit so I'd guess Nico is correct. >>> >> >> Yes, Nico is correct, as I already answered, however it is not any >> change of stsi(15) but a change of stsi(15.1.2) output which sets the >> change bit. > > hum, that is what the POP says but in fact you are right a change of > topology that changes the output of any STSI(15) sets the topology > change report bit as the output of STSI(15.1.2) would be changed too > obviously.
In this case I was just being too lazy to look up the correct query code but I knew it started with fc 15. It was Friday after all :-)
> > Regards, > Pierre >
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