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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/14/24 04:45, maobibo wrote: > I do not know whether KVM_DIRTY_LOG_INITIALLY_SET should be enabled on > LoongArch. If it is set, write protection for second MMU will start one > by one in function kvm_arch_mmu_enable_log_dirty_pt_masked() when dirty > log is cleared if it is set, else write protection will start in > function kvm_arch_commit_memory_region() when flag of memslot is changed. > > I do not see the obvious benefits between these two write protect > stages. Can anyone give me any hints? The advantage is that you get (a lot) fewer vmexits to set the dirty bitmap, and that write protection is not done in a single expensive step. Instead it is done at the time that userspace first clears the bits in the dirty bitmap. It provides much better performance. Paolo