> From: Paolo Bonzini [mailto:pbonz...@redhat.com] > On 26/01/2017 14:37, Pavel Dovgalyuk wrote: > >> Simpler: > >> > >> use_icount && > >> ((int32_t)cpu->icount_decr.u32 < 0 || > >> cpu->icount_decr.u16.low + cpu->icount_extra == 0) > > Right. > > > >> But I'm not sure that you need to test u32. After all you're not > > Checking u32 is needed, because sometimes it is less than zero. > > If cpu->icount_decr.u32 is less than zero, the next translation block > would immediately exit with TB_EXIT_ICOUNT_EXPIRED, causing > > cpu->exception_index = EXCP_INTERRUPT; > *last_tb = NULL; > cpu_loop_exit(cpu); > > from cpu_loop_exec_tb's "case TB_EXIT_ICOUNT_EXPIRED". > > And the same is true for cpu->icount_decr.u16.low + cpu->icount_extra == > 0, so I don't understand why this part of the patch is necessary.
I removed that lines because we have to check icount=0 not only when it is expired, but also when all instructions were executed successfully. If there are no instructions to execute, calling tb_find (and translation then) may cause an exception at the wrong moment. Pavel Dovgalyuk
