Messages in this thread | | | Date | Fri, 18 Feb 2022 14:13:34 +0100 | Subject | Re: [PATCH v7 1/1] s390x: KVM: guest support for topology function | From | Pierre Morel <> |
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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 > [...] >> >> -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.
> > [...] >> 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? >
You are right, we should look at the drawer and book id too. Something like that I think:
if ((topology_physical_package_id(vcpu->cpu) != topology_physical_package_id(vcpu->arch.prev_cpu)) || (topology_book_id(vcpu->cpu) != topology_book_id(vcpu->arch.prev_cpu)) || (topology_drawer_id(vcpu->cpu) != topology_drawer_id(vcpu->arch.prev_cpu))) return true;
Thanks, regards, Pierre -- Pierre Morel IBM Lab Boeblingen
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