Re: [Qemu-devel] [PATCH v6 3/7] trace: [tcg] Delay changes to dynamic state when translating

[Paolo Bonzini <pbonzini@redhat.com>]

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On 09/01/2017 18:01, Stefan Hajnoczi wrote:
> Or use a simpler scheme:
> 
> struct CPUState {
>     ...
>     uint32_t dstate_update_count;
> };
> 
> In trace_event_set_vcpu_state_dynamic():
> 
>     if (state) {
>         trace_events_enabled_count++;
>         set_bit(vcpu_id, vcpu->trace_dstate_delayed);
> 	atomic_inc(&vcpu->dstate_update_count, 1);
>         (*ev->dstate)++;
>     } ...
> 
> In cpu_exec() and friends:
> 
>     last_dstate_update_count = atomic_read(&vcpu->dstate_update_count);
> 
>     tb = tb_find(cpu, last_tb, tb_exit);
>     cpu_loop_exec_tb(cpu, tb, &last_tb, &tb_exit, &sc);
> 
>     /* apply and disable delayed dstate changes */
>     if (unlikely(atomic_read(&cpu->dstate_update_count) != last_dstate_update_count)) {
>         bitmap_copy(cpu->trace_dstate, cpu->trace_dstate_delayed,
>         trace_get_vcpu_event_count());
>     }
> 
> (You'll need to adjust the details but the update counter approach
> should be workable.)

Would it work to use async_run_on_cpu?

Thanks,

Paolo


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