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    SubjectRe: [PATCH v4 1/2] KVM: remove NULL return path for vcpu ids >= KVM_MAX_VCPUS
    > Commit c896939f7cff ("KVM: use heuristic for fast VCPU lookup by id") added
    > a return path that prevents vcpu ids to exceed KVM_MAX_VCPUS. This is a
    > problem for powerpc where vcpu ids can grow up to 8*KVM_MAX_VCPUS.
    >
    > This patch simply reverses the logic so that we only try fast path if the
    > vcpu id can be tried as an index in kvm->vcpus[]. The slow path is not
    > affected by the change.
    >
    > Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
    > ---
    > include/linux/kvm_host.h | 7 ++++---
    > 1 file changed, 4 insertions(+), 3 deletions(-)
    >
    > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
    > index 5276fe0916fc..23bfe1bd159c 100644
    > --- a/include/linux/kvm_host.h
    > +++ b/include/linux/kvm_host.h
    > @@ -447,12 +447,13 @@ static inline struct kvm_vcpu *kvm_get_vcpu(struct kvm *kvm, int i)
    >
    > static inline struct kvm_vcpu *kvm_get_vcpu_by_id(struct kvm *kvm, int id)
    > {
    > - struct kvm_vcpu *vcpu;
    > + struct kvm_vcpu *vcpu = NULL;
    > int i;
    >
    > - if (id < 0 || id >= KVM_MAX_VCPUS)
    > + if (id < 0)
    > return NULL;
    > - vcpu = kvm_get_vcpu(kvm, id);
    > + if (id < KVM_MAX_VCPUS)
    > + vcpu = kvm_get_vcpu(kvm, id);

    Maybe this check even should go into kvm_get_vcpu()

    > if (vcpu && vcpu->vcpu_id == id)
    > return vcpu;
    > kvm_for_each_vcpu(i, vcpu, kvm)
    >

    Anyhow,

    Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>

    David

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