• Janosch Frank's avatar
    KVM: s390: Add huge page enablement control · a4499382
    Janosch Frank authored
    General KVM huge page support on s390 has to be enabled via the
    kvm.hpage module parameter. Either nested or hpage can be enabled, as
    we currently do not support vSIE for huge backed guests. Once the vSIE
    support is added we will either drop the parameter or enable it as
    default.
    
    For a guest the feature has to be enabled through the new
    KVM_CAP_S390_HPAGE_1M capability and the hpage module
    parameter. Enabling it means that cmm can't be enabled for the vm and
    disables pfmf and storage key interpretation.
    
    This is due to the fact that in some cases, in upcoming patches, we
    have to split huge pages in the guest mapping to be able to set more
    granular memory protection on 4k pages. These split pages have fake
    page tables that are not visible to the Linux memory management which
    subsequently will not manage its PGSTEs, while the SIE will. Disabling
    these features lets us manage PGSTE data in a consistent matter and
    solve that problem.
    Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
    Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
    a4499382
api.txt 154 KB