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

[Joao Martins <joao.m.martins@oracle.com>]

On 7/4/19 12:51 AM, Marcelo Tosatti wrote:
> +++ 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;
> +

Isn't this meant to return -ENODEV value if the module is meant to not load?

Also this check should probably be placed before initializing the poll state,
provided poll state isn't used anyways if you're not a kvm guest.

	Joao