• Thomas Huth's avatar
    KVM: s390: Do not report unusabled IDs via KVM_CAP_MAX_VCPU_ID · 527919d0
    Thomas Huth authored
    commit a86cb413f4bf273a9d341a3ab2c2ca44e12eb317 upstream.
    KVM_CAP_MAX_VCPU_ID is currently always reporting KVM_MAX_VCPU_ID on all
    architectures. However, on s390x, the amount of usable CPUs is determined
    during runtime - it is depending on the features of the machine the code
    is running on. Since we are using the vcpu_id as an index into the SCA
    structures that are defined by the hardware (see e.g. the sca_add_vcpu()
    function), it is not only the amount of CPUs that is limited by the hard-
    ware, but also the range of IDs that we can use.
    Thus KVM_CAP_MAX_VCPU_ID must be determined during runtime on s390x, too.
    So the handling of KVM_CAP_MAX_VCPU_ID has to be moved from the common
    code into the architecture specific code, and on s390x we have to return
    the same value here as for KVM_CAP_MAX_VCPUS.
    This problem has been discovered with the kvm_create_max_vcpus selftest.
    With this change applied, the selftest now passes on s390x, too.
    Reviewed-by: 's avatarAndrew Jones <drjones@redhat.com>
    Reviewed-by: 's avatarCornelia Huck <cohuck@redhat.com>
    Reviewed-by: 's avatarDavid Hildenbrand <david@redhat.com>
    Signed-off-by: 's avatarThomas Huth <thuth@redhat.com>
    Message-Id: <20190523164309.13345-9-thuth@redhat.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: 's avatarChristian Borntraeger <borntraeger@de.ibm.com>
    Signed-off-by: 's avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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