I guess you are trying to fix the sympthoms of the case when iothread is trying to access instruction count.
Maybe the solution is providing access to current_cpu for the iothread coupled with your patch 8? Pavel Dovgalyuk > -----Original Message----- > From: Alex Bennée [mailto:alex.ben...@linaro.org] > Sent: Monday, April 03, 2017 3:45 PM > To: dovga...@ispras.ru; r...@twiddle.net; pbonz...@redhat.com > Cc: peter.mayd...@linaro.org; qemu-devel@nongnu.org; > mt...@listserver.greensocs.com; > fred.kon...@greensocs.com; a.r...@virtualopensystems.com; c...@braap.org; > bobby.pr...@gmail.com; nik...@linux.vnet.ibm.com; Alex Bennée; Peter > Crosthwaite > Subject: [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu > > As icount is only supported for single-threaded execution due to the > requirement for determinism let's remove it from the common > tcg_exec_cpu path. > > Also remove the additional fiddling which shouldn't be required as the > icount counters should all be rectified as you enter the loop. > > Signed-off-by: Alex Bennée <alex.ben...@linaro.org> > --- > cpus.c | 67 > +++++++++++++++++++++++++++++++++++++++++++++--------------------- > 1 file changed, 46 insertions(+), 21 deletions(-) > > diff --git a/cpus.c b/cpus.c > index 18b1746770..87638a75d2 100644 > --- a/cpus.c > +++ b/cpus.c > @@ -1179,47 +1179,66 @@ static void handle_icount_deadline(void) > } > } > > -static int tcg_cpu_exec(CPUState *cpu) > +static void prepare_icount_for_run(CPUState *cpu) > { > - int ret; > -#ifdef CONFIG_PROFILER > - int64_t ti; > -#endif > - > -#ifdef CONFIG_PROFILER > - ti = profile_getclock(); > -#endif > if (use_icount) { > int64_t count; > int decr; > - timers_state.qemu_icount -= (cpu->icount_decr.u16.low > - + cpu->icount_extra); > - cpu->icount_decr.u16.low = 0; > - cpu->icount_extra = 0; > + > + /* These should always be cleared by process_icount_data after > + * each vCPU execution. However u16.high can be raised > + * asynchronously by cpu_exit/cpu_interrupt/tcg_handle_interrupt > + */ > + g_assert(cpu->icount_decr.u16.low == 0); > + g_assert(cpu->icount_extra == 0); > + > + > count = tcg_get_icount_limit(); > + > timers_state.qemu_icount += count; > decr = (count > 0xffff) ? 0xffff : count; > count -= decr; > cpu->icount_decr.u16.low = decr; > cpu->icount_extra = count; > } > - qemu_mutex_unlock_iothread(); > - cpu_exec_start(cpu); > - ret = cpu_exec(cpu); > - cpu_exec_end(cpu); > - qemu_mutex_lock_iothread(); > -#ifdef CONFIG_PROFILER > - tcg_time += profile_getclock() - ti; > -#endif > +} > + > +static void process_icount_data(CPUState *cpu) > +{ > if (use_icount) { > /* Fold pending instructions back into the > instruction counter, and clear the interrupt flag. */ > timers_state.qemu_icount -= (cpu->icount_decr.u16.low > + cpu->icount_extra); > + > + /* We must be under BQL here as cpu_exit can tweak > + icount_decr.u32 */ > + g_assert(qemu_mutex_iothread_locked()); > cpu->icount_decr.u32 = 0; > cpu->icount_extra = 0; > replay_account_executed_instructions(); > } > +} > + > + > +static int tcg_cpu_exec(CPUState *cpu) > +{ > + int ret; > +#ifdef CONFIG_PROFILER > + int64_t ti; > +#endif > + > +#ifdef CONFIG_PROFILER > + ti = profile_getclock(); > +#endif > + qemu_mutex_unlock_iothread(); > + cpu_exec_start(cpu); > + ret = cpu_exec(cpu); > + cpu_exec_end(cpu); > + qemu_mutex_lock_iothread(); > +#ifdef CONFIG_PROFILER > + tcg_time += profile_getclock() - ti; > +#endif > return ret; > } > > @@ -1306,7 +1325,13 @@ static void *qemu_tcg_rr_cpu_thread_fn(void *arg) > > if (cpu_can_run(cpu)) { > int r; > + > + prepare_icount_for_run(cpu); > + > r = tcg_cpu_exec(cpu); > + > + process_icount_data(cpu); > + > if (r == EXCP_DEBUG) { > cpu_handle_guest_debug(cpu); > break; > -- > 2.11.0
