Re: [Xen-devel] Interrupt injection with ISR set on Intel hardware

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.12.18 at 02:28, <kevin.tian@xxxxxxxxx> wrote:
> btw I checked your original mail:
> 
> (XEN)    [<ffff82d0802e2403>] mwait-idle.c#mwait_idle+0x2a5/0x381
> xen/arch/x86/cpu/mwait-idle.c:802
> 
>    788                if (cpu_is_haltable(cpu))
>    789                        mwait_idle_with_hints(eax, 
> MWAIT_ECX_INTERRUPT_BREAK);
>    790
>    791                after = cpuidle_get_tick();
>    792
>    793                cstate_restore_tsc();
>    794                trace_exit_reason(irq_traced);
>    795                TRACE_6D(TRC_PM_IDLE_EXIT, cx->type, after,
>    796                        irq_traced[0], irq_traced[1], irq_traced[2], 
> irq_traced[3]);
>    797
>    798                /* Now back in C0. */
>    799                update_idle_stats(power, cx, before, after);
>    800                local_irq_enable();
>    801
> -> 802                if (!(lapic_timer_reliable_states & (1 << cstate)))
>    803                        lapic_timer_on();
>    804
>    805                sched_tick_resume();
>    806                cpufreq_dbs_timer_resume();
> 
> Looks above code is different from staging:
> 
> acpi_processor_idle:
>       acpi_idle_do_entry:
>               acpi_processor_ffh_cstate_enter:
>                       mwait_idle_with_hints
> 
> there is no mwait_idle alone. and even with compiler optimization I didn't
> find code sequence like above...

You're looking at two entirely different code paths, only one of
which can be in use in any particular case: Either the idle
entering routine used is acpi_processor_idle(), or (when the
processor is supported by that driver code) it is mwait_idle().
See mwait_idle_init() for when the latter gets used; the former
may get installed at the point the Dom0 kernel reports ACPI
C-state data (and only when mwait_idle() is not in use).

Jan



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