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Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of
From: |
Pavel Dovgalyuk |
Subject: |
Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu |
Date: |
Tue, 4 Apr 2017 08:39:53 +0300 |
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:address@hidden
> Sent: Monday, April 03, 2017 3:45 PM
> To: address@hidden; address@hidden; address@hidden
> Cc: address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; address@hidden;
> address@hidden; address@hidden; 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 <address@hidden>
> ---
> 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
- [Qemu-devel] [RFC PATCH v1 0/9] MTTCG and record/replay fixes for rc3, Alex Bennée, 2017/04/03
- [Qemu-devel] [RFC PATCH v1 5/9] cpus: remove icount handling from qemu_tcg_cpu_thread_fn, Alex Bennée, 2017/04/03
- [Qemu-devel] [RFC PATCH v1 1/9] scripts/qemugdb/mtree.py: fix up mtree dump, Alex Bennée, 2017/04/03
- [Qemu-devel] [RFC PATCH v1 2/9] scripts/qemu-gdb/timers.py: new helper to dump timer state, Alex Bennée, 2017/04/03
- [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/03
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu,
Pavel Dovgalyuk <=
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Paolo Bonzini, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Paolo Bonzini, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/04
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Pavel Dovgalyuk, 2017/04/05
- Re: [Qemu-devel] [RFC PATCH v1 7/9] cpus: move icount preparation out of tcg_exec_cpu, Alex Bennée, 2017/04/05
[Qemu-devel] [RFC PATCH v1 6/9] cpus: check cpu->running in cpu_get_icount_raw(), Alex Bennée, 2017/04/03