Re: [patch 1/5] add cpuidle-haltpoll driver

["Rafael J. Wysocki" <rafael@kernel.org>]

On Mon, Jul 1, 2019 at 8:57 PM Marcelo Tosatti <mtosatti@redhat.com> wrote:
>
> Add a cpuidle driver that calls the architecture default_idle routine.
>
> To be used in conjunction with the haltpoll governor.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

>
> ---
>  arch/x86/kernel/process.c          |    2 -
>  drivers/cpuidle/Kconfig            |    9 +++++
>  drivers/cpuidle/Makefile           |    1
>  drivers/cpuidle/cpuidle-haltpoll.c |   65 +++++++++++++++++++++++++++++++++++++
>  4 files changed, 76 insertions(+), 1 deletion(-)
>
> Index: linux-2.6-newcpuidle.git/arch/x86/kernel/process.c
> ===================================================================
> --- linux-2.6-newcpuidle.git.orig/arch/x86/kernel/process.c
> +++ linux-2.6-newcpuidle.git/arch/x86/kernel/process.c
> @@ -580,7 +580,7 @@ void __cpuidle default_idle(void)
>         safe_halt();
>         trace_cpu_idle_rcuidle(PWR_EVENT_EXIT, smp_processor_id());
>  }
> -#ifdef CONFIG_APM_MODULE
> +#if defined(CONFIG_APM_MODULE) || defined(CONFIG_HALTPOLL_CPUIDLE_MODULE)
>  EXPORT_SYMBOL(default_idle);
>  #endif
>
> Index: linux-2.6-newcpuidle.git/drivers/cpuidle/Kconfig
> ===================================================================
> --- linux-2.6-newcpuidle.git.orig/drivers/cpuidle/Kconfig
> +++ linux-2.6-newcpuidle.git/drivers/cpuidle/Kconfig
> @@ -51,6 +51,15 @@ depends on PPC
>  source "drivers/cpuidle/Kconfig.powerpc"
>  endmenu
>
> +config HALTPOLL_CPUIDLE
> +       tristate "Halt poll cpuidle driver"
> +       depends on X86 && KVM_GUEST
> +       default y
> +       help
> +         This option enables halt poll cpuidle driver, which allows to poll
> +         before halting in the guest (more efficient than polling in the
> +         host via halt_poll_ns for some scenarios).
> +
>  endif
>
>  config ARCH_NEEDS_CPU_IDLE_COUPLED
> Index: linux-2.6-newcpuidle.git/drivers/cpuidle/Makefile
> ===================================================================
> --- linux-2.6-newcpuidle.git.orig/drivers/cpuidle/Makefile
> +++ linux-2.6-newcpuidle.git/drivers/cpuidle/Makefile
> @@ -7,6 +7,7 @@ obj-y += cpuidle.o driver.o governor.o s
>  obj-$(CONFIG_ARCH_NEEDS_CPU_IDLE_COUPLED) += coupled.o
>  obj-$(CONFIG_DT_IDLE_STATES)             += dt_idle_states.o
>  obj-$(CONFIG_ARCH_HAS_CPU_RELAX)         += poll_state.o
> +obj-$(CONFIG_HALTPOLL_CPUIDLE)           += cpuidle-haltpoll.o
>
>  ##################################################################################
>  # ARM SoC drivers
> Index: linux-2.6-newcpuidle.git/drivers/cpuidle/cpuidle-haltpoll.c
> ===================================================================
> --- /dev/null
> +++ linux-2.6-newcpuidle.git/drivers/cpuidle/cpuidle-haltpoll.c
> @@ -0,0 +1,69 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * cpuidle driver for haltpoll governor.
> + *
> + * Copyright 2019 Red Hat, Inc. and/or its affiliates.
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.  See
> + * the COPYING file in the top-level directory.
> + *
> + * Authors: Marcelo Tosatti <mtosatti@redhat.com>
> + */
> +
> +#include <linux/init.h>
> +#include <linux/cpuidle.h>
> +#include <linux/module.h>
> +#include <linux/sched/idle.h>
> +#include <linux/kvm_para.h>
> +
> +static int default_enter_idle(struct cpuidle_device *dev,
> +                             struct cpuidle_driver *drv, int index)
> +{
> +       if (current_clr_polling_and_test()) {
> +               local_irq_enable();
> +               return index;
> +       }
> +       default_idle();
> +       return index;
> +}
> +
> +static struct cpuidle_driver haltpoll_driver = {
> +       .name = "haltpoll",
> +       .owner = THIS_MODULE,
> +       .states = {
> +               { /* entry 0 is for polling */ },
> +               {
> +                       .enter                  = default_enter_idle,
> +                       .exit_latency           = 1,
> +                       .target_residency       = 1,
> +                       .power_usage            = -1,
> +                       .name                   = "haltpoll idle",
> +                       .desc                   = "default architecture idle",
> +               },
> +       },
> +       .safe_state_index = 0,
> +       .state_count = 2,
> +};
> +
> +static int __init haltpoll_init(void)
> +{
> +       struct cpuidle_driver *drv = &haltpoll_driver;
> +
> +       cpuidle_poll_state_init(drv);
> +
> +       if (!kvm_para_available())
> +               return 0;
> +
> +       return cpuidle_register(&haltpoll_driver, NULL);
> +}
> +
> +static void __exit haltpoll_exit(void)
> +{
> +       cpuidle_unregister(&haltpoll_driver);
> +}
> +
> +module_init(haltpoll_init);
> +module_exit(haltpoll_exit);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
> +
>
>