Virtualization - Jun 2022 - [PATCH 04/36] cpuidle,intel_idle: Fix CPUIDLE_FLAG_IRQ_ENABLE

On Wed, Jun 8, 2022 at 4:47 PM Peter Zijlstra <peterz at infradead.org>
wrote:
>
> Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
> Xeons") wrecked intel_idle in two ways:
>
>  - must not have tracing in idle functions
>  - must return with IRQs disabled
>
> Additionally, it added a branch for no good reason.
>
> Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on
Xeons")
> Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>

And do I think correctly that this can be applied without the rest of
the series?
> ---
>  drivers/idle/intel_idle.c |   48
+++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 37 insertions(+), 11 deletions(-)
>
> --- a/drivers/idle/intel_idle.c
> +++ b/drivers/idle/intel_idle.c
> @@ -129,21 +137,37 @@ static unsigned int mwait_substates __in
>   *
>   * Must be called under local_irq_disable().
>   */
> +
> -static __cpuidle int intel_idle(struct cpuidle_device *dev,
> -                               struct cpuidle_driver *drv, int index)
> +static __always_inline int __intel_idle(struct cpuidle_device *dev,
> +                                       struct cpuidle_driver *drv, int
index)
>  {
>         struct cpuidle_state *state = &drv->states[index];
>         unsigned long eax = flg2MWAIT(state->flags);
>         unsigned long ecx = 1; /* break on interrupt flag */
>
> -       if (state->flags & CPUIDLE_FLAG_IRQ_ENABLE)
> -               local_irq_enable();
> -
>         mwait_idle_with_hints(eax, ecx);
>
>         return index;
>  }
>
> +static __cpuidle int intel_idle(struct cpuidle_device *dev,
> +                               struct cpuidle_driver *drv, int index)
> +{
> +       return __intel_idle(dev, drv, index);
> +}
> +
> +static __cpuidle int intel_idle_irq(struct cpuidle_device *dev,
> +                                   struct cpuidle_driver *drv, int index)
> +{
> +       int ret;
> +
> +       raw_local_irq_enable();
> +       ret = __intel_idle(dev, drv, index);
> +       raw_local_irq_disable();
> +
> +       return ret;
> +}
> +
>  /**
>   * intel_idle_s2idle - Ask the processor to enter the given idle state.
>   * @dev: cpuidle device of the target CPU.
> @@ -1801,6 +1824,9 @@ static void __init intel_idle_init_cstat
>                 /* Structure copy. */
>                 drv->states[drv->state_count] =
cpuidle_state_table[cstate];
>
> +               if (cpuidle_state_table[cstate].flags &
CPUIDLE_FLAG_IRQ_ENABLE)
> +                       drv->states[drv->state_count].enter =
intel_idle_irq;
> +
>                 if ((disabled_states_mask & BIT(drv->state_count))
||
>                     ((icpu->use_acpi || force_use_acpi) &&
>                      intel_idle_off_by_default(mwait_hint) &&
>
>

On Wed, Jun 08, 2022 at 05:01:05PM +0200, Rafael J. Wysocki
wrote:
> On Wed, Jun 8, 2022 at 4:47 PM Peter Zijlstra <peterz at
infradead.org> wrote:
> >
> > Commit c227233ad64c ("intel_idle: enable interrupts before C1 on
> > Xeons") wrecked intel_idle in two ways:
> >
> >  - must not have tracing in idle functions
> >  - must return with IRQs disabled
> >
> > Additionally, it added a branch for no good reason.
> >
> > Fixes: c227233ad64c ("intel_idle: enable interrupts before C1 on
Xeons")
> > Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
> 
> Acked-by: Rafael J. Wysocki <rafael.j.wysocki at intel.com>
> 
> And do I think correctly that this can be applied without the rest of
> the series?
Yeah, I don't think this relies on any of the preceding patches. If you
want to route this through the pm/fixes tree that's fine.

Thanks!