• Paul Mackerras's avatar
    KVM: PPC: Book3S HV: Make the guest hash table size configurable · 32fad281
    Paul Mackerras authored
    This adds a new ioctl to enable userspace to control the size of the guest
    hashed page table (HPT) and to clear it out when resetting the guest.
    The KVM_PPC_ALLOCATE_HTAB ioctl is a VM ioctl and takes as its parameter
    a pointer to a u32 containing the desired order of the HPT (log base 2
    of the size in bytes), which is updated on successful return to the
    actual order of the HPT which was allocated.
    There must be no vcpus running at the time of this ioctl.  To enforce
    this, we now keep a count of the number of vcpus running in
    If the ioctl is called when a HPT has already been allocated, we don't
    reallocate the HPT but just clear it out.  We first clear the
    kvm->arch.rma_setup_done flag, which has two effects: (a) since we hold
    the kvm->lock mutex, it will prevent any vcpus from starting to run until
    we're done, and (b) it means that the first vcpu to run after we're done
    will re-establish the VRMA if necessary.
    If userspace doesn't call this ioctl before running the first vcpu, the
    kernel will allocate a default-sized HPT at that point.  We do it then
    rather than when creating the VM, as the code did previously, so that
    userspace has a chance to do the ioctl if it wants.
    When allocating the HPT, we can allocate either from the kernel page
    allocator, or from the preallocated pool.  If userspace is asking for
    a different size from the preallocated HPTs, we first try to allocate
    using the kernel page allocator.  Then we try to allocate from the
    preallocated pool, and then if that fails, we try allocating decreasing
    sizes from the kernel page allocator, down to the minimum size allowed
    (256kB).  Note that the kernel page allocator limits allocations to
    1 << CONFIG_FORCE_MAX_ZONEORDER pages, which by default corresponds to
    16MB (on 64-bit powerpc, at least).
    Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
    [agraf: fix module compilation]
    Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
kvm.h 26.5 KB