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

Rafael J. Wysocki
2019-06-25T21:50:18Z

On Fri, Jun 14, 2019 at 12:55 AM 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>
>
> ---
> 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.git/arch/x86/kernel/process.c
> ===================================================================
> --- linux-2.6.git.orig/arch/x86/kernel/process.c 2019-06-13 16:19:27.877064340 -0400
> +++ linux-2.6.git/arch/x86/kernel/process.c 2019-06-13 16:19:48.795544892 -0400
> @@ -580,7 +580,7 @@
> 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.git/drivers/cpuidle/Kconfig
> ===================================================================
> --- linux-2.6.git.orig/drivers/cpuidle/Kconfig 2019-06-13 16:19:27.878064316 -0400
> +++ linux-2.6.git/drivers/cpuidle/Kconfig 2019-06-13 18:41:40.599912671 -0400
> @@ -51,6 +51,15 @@
> source "drivers/cpuidle/Kconfig.powerpc"
> endmenu
>
> +config HALTPOLL_CPUIDLE
> + tristate "Halt poll cpuidle driver"
> + depends on X86
> + 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.git/drivers/cpuidle/Makefile
> ===================================================================
> --- linux-2.6.git.orig/drivers/cpuidle/Makefile 2019-06-13 16:19:27.878064316 -0400
> +++ linux-2.6.git/drivers/cpuidle/Makefile 2019-06-13 16:19:48.796544867 -0400
> @@ -7,6 +7,7 @@
> 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.git/drivers/cpuidle/cpuidle-haltpoll.c
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.git/drivers/cpuidle/cpuidle-haltpoll.c 2019-06-13 18:41:39.305933413 -0400
> @@ -0,0 +1,65 @@
> +// 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>
> +
> +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 = 0,
> + .target_residency = 0,
> + .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);
> +
> + return cpuidle_register(&haltpoll_driver, NULL);

Would it be practical to prevent this driver from loading on non-virt?

> +}
> +
> +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>");
> +

Apart from the above it is simple enough.