On Mon, Jan 16, 2017 at 9:19 AM, Paolo Bonzini <pbonz...@redhat.com> wrote: > On 12/01/2017 13:19, Pavel Dovgalyuk wrote: >>> From: Peter Maydell [mailto:peter.mayd...@linaro.org] >>> On 12 January 2017 at 11:28, Pavel Dovgalyuk <dovga...@ispras.ru> wrote: >>>>> From: Max Filippov [mailto:jcmvb...@gmail.com] >>>>> Ok, looks like what happens in my case is that instruction that >>>>> sets CCOMPARE and thus changes remaining icount does not >>>>> cause exit from the cpu_exec. So merely ending TB on >>>>> QEMU_CLOCK_VIRTUAL timer update is not enough, I need to >>>>> throw an exception of some kind? Or does the timer code need >>>>> to take care of that? >>>> >>>> Yes, it seems that you should end the block with an exception, >>>> to allow icount loop recalculate the timeouts. >>> >>> Really? The ARM translate.c doesn't generate an exception. >>> It just does >>> gen_io_end(); >>> gen_lookup_tb(); >>> >>> (so we force a lookup of the next TB, but don't throw an >>> exception of any kind). >> >> Maybe I missing something. As far as I understand, changing the virtual timer >> notifies the iothread and os_host_main_loop_wait kicks the CPU thread. >> >> But within that period of time before changing the timer and kicking the >> thread >> CPU may proceed some instructions and the timer will be expired if it was set >> to one of the soonest instructions. > > My understanding (which may be wrong!) was that after gen_io_end you > would exit with TB_EXIT_ICOUNT_EXPIRED and cpu->icount_decr.u16.high = > -1, but indeed I don't see anything that calls cpu_interrupt in that > path. > > Maybe something like this: > > diff --git a/include/exec/gen-icount.h b/include/exec/gen-icount.h > index 050de59..c20d193 100644 > --- a/include/exec/gen-icount.h > +++ b/include/exec/gen-icount.h > @@ -73,6 +73,9 @@ static inline void gen_io_end(void) > { > TCGv_i32 tmp = tcg_const_i32(0); > tcg_gen_st_i32(tmp, cpu_env, -ENV_OFFSET + offsetof(CPUState, > can_do_io)); > + /* Make the next TB exit immediately with TB_EXIT_ICOUNT_EXPIRED. */ > + tcg_gen_st16_i32(-1, cpu_env, > + -ENV_OFFSET + offsetof(CPUState, icount_decr.u16.high)); > tcg_temp_free_i32(tmp); > }
With -1 moved into TCG temporary that works for me as well. -- Thanks. -- Max
