Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Fri, Sep 03, 2021, Vitaly Kuznetsov wrote: >> Jiang Jiasheng <jiasheng@xxxxxxxxxxx> writes: >> >> > The kvm_get_vcpu() will call for the array_index_nospec() >> > with the value of atomic_read(&(v->kvm)->online_vcpus) as size, >> > and the value of constant '0' as index. >> > If the size is also '0', it will be unreasonabe >> > that the index is no less than the size. >> > >> >> Can this really happen? >> >> 'online_vcpus' is never decreased, it is increased with every >> kvm_vm_ioctl_create_vcpu() call when a new vCPU is created and is set to >> 0 when all vCPUs are destroyed (kvm_free_vcpus()). >> >> kvm_guest_time_update() takes a vcpu as a parameter, this means that at >> least 1 vCPU is currently present so 'online_vcpus' just can't be zero. > > Agreed, but doing kvm_get_vcpu() is ugly and overkill. > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 86539c1686fa..cc1cb9a401cd 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -2969,7 +2969,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v) > offsetof(struct compat_vcpu_info, time)); > if (vcpu->xen.vcpu_time_info_set) > kvm_setup_pvclock_page(v, &vcpu->xen.vcpu_time_info_cache, 0); > - if (v == kvm_get_vcpu(v->kvm, 0)) > + if (!kvm_vcpu_get_idx(v)) Do we really need to keep kvm_vcpu_get_idx() around though? It has only 3 users, all in arch/x86/kvm/hyperv.[ch], and the inline simpy returns 'vcpu->vcpu_idx'. > kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock); > return 0; > } > -- Vitaly
