On 06/19/2013 07:32 PM, Paolo Bonzini wrote: > Il 19/06/2013 11:09, Xiao Guangrong ha scritto: >> Document it to Documentation/virtual/kvm/mmu.txt > > While reviewing the docs, I looked at the code. > > Why can't this happen? > > CPU 1: __get_spte_lockless CPU 2: __update_clear_spte_slow > ------------------------------------------------------------------------------ > write low > read count > read low > read high > write high > check low and count > update count > > The check passes, but CPU 1 read a "torn" SPTE. In this case, CPU 1 will read the "new low bits" and the "old high bits", right? the P bit in the low bits is cleared when do __update_clear_spte_slow, i.e, it is not present, so the whole value is ignored. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
