On Wed, Feb 09, 2022, Paolo Bonzini wrote: > The TDP MMU has a performance regression compared to the legacy MMU > when CR0 changes often. This was reported for the grsecurity kernel, > which uses CR0.WP to implement kernel W^X. In that case, each change to > CR0.WP unloads the MMU and causes a lot of unnecessary work. When running > nested, this can even cause the L1 to hardly make progress, as the L0 > hypervisor it is overwhelmed by the amount of MMU work that is needed. FWIW, my flushing/zapping series fixes this by doing the teardown in an async worker. There's even a selftest for this exact case :-) https://lore.kernel.org/all/20211223222318.1039223-1-seanjc@xxxxxxxxxx
