• Paolo Bonzini's avatar
    KVM: x86: fix nested guest live migration with PML · 1f4e5fc8
    Paolo Bonzini authored
    Shadow paging is fundamentally incompatible with the page-modification
    log, because the GPAs in the log come from the wrong memory map.
    In particular, for the EPT page-modification log, the GPAs in the log come
    from L2 rather than L1.  (If there was a non-EPT page-modification log,
    we couldn't use it for shadow paging because it would log GVAs rather
    than GPAs).
    
    Therefore, we need to rely on write protection to record dirty pages.
    This has the side effect of bypassing PML, since writes now result in an
    EPT violation vmexit.
    
    This is relatively easy to add to KVM, because pretty much the only place
    that needs changing is spte_clear_dirty.  The first access to the page
    already goes through the page fault path and records the correct GPA;
    it's only subsequent accesses that are wrong.  Therefore, we can equip
    set_spte (where the first access happens) to record that the SPTE will
    have to be write protected, and then spte_clear_dirty will use this
    information to do the right thing.
    Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
    1f4e5fc8
mmu.c 164 KB