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

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Thursday, December 13, 2018 4:37 PM
> 
> >>> 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).
> 

yes, I missed the other path.

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