Merge branch 'pm-cpuidle'

Guest halt polling

==================

The cpuidle_haltpoll driver, with the haltpoll governor, allows

the guest vcpus to poll for a specified amount of time before

halting.

This provides the following benefits to host side polling:

	1) The POLL flag is set while polling is performed, which allows

	   a remote vCPU to avoid sending an IPI (and the associated

	   cost of handling the IPI) when performing a wakeup.

	2) The VM-exit cost can be avoided.

The downside of guest side polling is that polling is performed

even with other runnable tasks in the host.

The basic logic as follows: A global value, guest_halt_poll_ns,

is configured by the user, indicating the maximum amount of

time polling is allowed. This value is fixed.

Each vcpu has an adjustable guest_halt_poll_ns

("per-cpu guest_halt_poll_ns"), which is adjusted by the algorithm

in response to events (explained below).

Module Parameters

=================

The haltpoll governor has 5 tunable module parameters:

1) guest_halt_poll_ns:

Maximum amount of time, in nanoseconds, that polling is

performed before halting.

Default: 200000

2) guest_halt_poll_shrink:

Division factor used to shrink per-cpu guest_halt_poll_ns when

wakeup event occurs after the global guest_halt_poll_ns.

Default: 2

3) guest_halt_poll_grow:

Multiplication factor used to grow per-cpu guest_halt_poll_ns

when event occurs after per-cpu guest_halt_poll_ns

but before global guest_halt_poll_ns.

Default: 2

4) guest_halt_poll_grow_start:

The per-cpu guest_halt_poll_ns eventually reaches zero

in case of an idle system. This value sets the initial

per-cpu guest_halt_poll_ns when growing. This can

be increased from 10000, to avoid misses during the initial

growth stage:

10k, 20k, 40k, ... (example assumes guest_halt_poll_grow=2).

Default: 50000

5) guest_halt_poll_allow_shrink:

Bool parameter which allows shrinking. Set to N

to avoid it (per-cpu guest_halt_poll_ns will remain

high once achieves global guest_halt_poll_ns value).

Default: Y

The module parameters can be set from the debugfs files in:

	/sys/module/haltpoll/parameters/

Further Notes

=============

- Care should be taken when setting the guest_halt_poll_ns parameter as a

large value has the potential to drive the cpu usage to 100% on a machine which

would be almost entirely idle otherwise.

	bool "KVM Guest support (including kvmclock)"

	depends on PARAVIRT

	select PARAVIRT_CLOCK

	select ARCH_CPUIDLE_HALTPOLL

	default y

	---help---

	  This option enables various optimizations for running under the KVM

	  underlying device model, the host provides the guest with

	  timing infrastructure such as time of day, and system time

config ARCH_CPUIDLE_HALTPOLL

        def_bool n

        prompt "Disable host haltpoll when loading haltpoll driver"

        help

	  If virtualized under KVM, disable host haltpoll.

config PVH

	bool "Support for running PVH guests"

	---help---

/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ARCH_HALTPOLL_H

#define _ARCH_HALTPOLL_H

void arch_haltpoll_enable(unsigned int cpu);

void arch_haltpoll_disable(unsigned int cpu);

#endif

{

	return cpuid_edx(kvm_cpuid_base() | KVM_CPUID_FEATURES);

}

EXPORT_SYMBOL_GPL(kvm_arch_para_hints);

static uint32_t __init kvm_detect(void)

{

}

#endif	/* CONFIG_PARAVIRT_SPINLOCKS */

#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL

static void kvm_disable_host_haltpoll(void *i)

{

	wrmsrl(MSR_KVM_POLL_CONTROL, 0);

}

static void kvm_enable_host_haltpoll(void *i)

{

	wrmsrl(MSR_KVM_POLL_CONTROL, 1);

}

void arch_haltpoll_enable(unsigned int cpu)

{

	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) {

		pr_err_once("kvm: host does not support poll control\n");

		pr_err_once("kvm: host upgrade recommended\n");

		return;

	}

	/* Enable guest halt poll disables host halt poll */

	smp_call_function_single(cpu, kvm_disable_host_haltpoll, NULL, 1);

}

EXPORT_SYMBOL_GPL(arch_haltpoll_enable);

void arch_haltpoll_disable(unsigned int cpu)

{

	if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL))

		return;

	/* Enable guest halt poll disables host halt poll */

	smp_call_function_single(cpu, kvm_enable_host_haltpoll, NULL, 1);

}

EXPORT_SYMBOL_GPL(arch_haltpoll_disable);

#endif

	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