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    KVM: PPC: Only get pages when actually needed, not in prepare_memory_region() · c77162de
    Paul Mackerras 提交于
    This removes the code from kvmppc_core_prepare_memory_region() that
    looked up the VMA for the region being added and called hva_to_page
    to get the pfns for the memory.  We have no guarantee that there will
    be anything mapped there at the time of the KVM_SET_USER_MEMORY_REGION
    ioctl call; userspace can do that ioctl and then map memory into the
    region later.
    
    Instead we defer looking up the pfn for each memory page until it is
    needed, which generally means when the guest does an H_ENTER hcall on
    the page.  Since we can't call get_user_pages in real mode, if we don't
    already have the pfn for the page, kvmppc_h_enter() will return
    H_TOO_HARD and we then call kvmppc_virtmode_h_enter() once we get back
    to kernel context.  That calls kvmppc_get_guest_page() to get the pfn
    for the page, and then calls back to kvmppc_h_enter() to redo the HPTE
    insertion.
    
    When the first vcpu starts executing, we need to have the RMO or VRMA
    region mapped so that the guest's real mode accesses will work.  Thus
    we now have a check in kvmppc_vcpu_run() to see if the RMO/VRMA is set
    up and if not, call kvmppc_hv_setup_rma().  It checks if the memslot
    starting at guest physical 0 now has RMO memory mapped there; if so it
    sets it up for the guest, otherwise on POWER7 it sets up the VRMA.
    The function that does that, kvmppc_map_vrma, is now a bit simpler,
    as it calls kvmppc_virtmode_h_enter instead of creating the HPTE itself.
    
    Since we are now potentially updating entries in the slot_phys[]
    arrays from multiple vcpu threads, we now have a spinlock protecting
    those updates to ensure that we don't lose track of any references
    to pages.
    Signed-off-by: NPaul Mackerras <paulus@samba.org>
    Signed-off-by: NAlexander Graf <agraf@suse.de>
    Signed-off-by: NAvi Kivity <avi@redhat.com>
    c77162de
book3s_64_mmu_hv.c 8.1 KB