[patch 5/5] cpuidle-haltpoll: disable host side polling when kvm virtualized

Marcelo Tosatti
2019-07-03T23:59:58Z

[-- Attachment #1: 04-pollcontrol-guest.patch --]
[-- Type: text/plain, Size: 4631 bytes --]

When performing guest side polling, it is not necessary to
also perform host side polling.

So disable host side polling, via the new MSR interface,
when loading cpuidle-haltpoll driver.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
arch/x86/Kconfig | 7 +++++
arch/x86/include/asm/cpuidle_haltpoll.h | 8 ++++++
arch/x86/kernel/kvm.c | 42 ++++++++++++++++++++++++++++++++
drivers/cpuidle/cpuidle-haltpoll.c | 10 ++++++-
include/linux/cpuidle_haltpoll.h | 16 ++++++++++++
5 files changed, 82 insertions(+), 1 deletion(-)

Index: kvm/arch/x86/include/asm/cpuidle_haltpoll.h
===================================================================
--- /dev/null
+++ kvm/arch/x86/include/asm/cpuidle_haltpoll.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ARCH_HALTPOLL_H
+#define _ARCH_HALTPOLL_H
+
+void arch_haltpoll_enable(void);
+void arch_haltpoll_disable(void);
+
+#endif
Index: kvm/drivers/cpuidle/cpuidle-haltpoll.c
===================================================================
--- kvm.orig/drivers/cpuidle/cpuidle-haltpoll.c
+++ kvm/drivers/cpuidle/cpuidle-haltpoll.c
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/sched/idle.h>
#include <linux/kvm_para.h>
+#include <linux/cpuidle_haltpoll.h>

static int default_enter_idle(struct cpuidle_device *dev,
struct cpuidle_driver *drv, int index)
@@ -47,6 +48,7 @@ static struct cpuidle_driver haltpoll_dr

static int __init haltpoll_init(void)
{
+ int ret;
struct cpuidle_driver *drv = &haltpoll_driver;

cpuidle_poll_state_init(drv);
@@ -54,11 +56,16 @@ static int __init haltpoll_init(void)
if (!kvm_para_available())
return 0;

- return cpuidle_register(&haltpoll_driver, NULL);
+ ret = cpuidle_register(&haltpoll_driver, NULL);
+ if (ret == 0)
+ arch_haltpoll_enable();
+
+ return ret;
}

static void __exit haltpoll_exit(void)
{
+ arch_haltpoll_disable();
cpuidle_unregister(&haltpoll_driver);
}

Index: kvm/include/linux/cpuidle_haltpoll.h
===================================================================
--- /dev/null
+++ kvm/include/linux/cpuidle_haltpoll.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _CPUIDLE_HALTPOLL_H
+#define _CPUIDLE_HALTPOLL_H
+
+#ifdef CONFIG_ARCH_CPUIDLE_HALTPOLL
+#include <asm/cpuidle_haltpoll.h>
+#else
+static inline void arch_haltpoll_enable(void)
+{
+}
+
+static inline void arch_haltpoll_disable(void)
+{
+}
+#endif
+#endif
Index: kvm/arch/x86/Kconfig
===================================================================
--- kvm.orig/arch/x86/Kconfig
+++ kvm/arch/x86/Kconfig
@@ -787,6 +787,7 @@ config KVM_GUEST
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
@@ -795,6 +796,12 @@ config KVM_GUEST
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---
Index: kvm/arch/x86/kernel/kvm.c
===================================================================
--- kvm.orig/arch/x86/kernel/kvm.c
+++ kvm/arch/x86/kernel/kvm.c
@@ -874,3 +874,45 @@ void __init kvm_spinlock_init(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(void)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL)) {
+ printk(KERN_ERR "kvm: host does not support poll control\n");
+ printk(KERN_ERR "kvm: host upgrade recommended\n");
+ return;
+ }
+
+ preempt_disable();
+ /* Enable guest halt poll disables host halt poll */
+ kvm_disable_host_haltpoll(NULL);
+ smp_call_function(kvm_disable_host_haltpoll, NULL, 1);
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(arch_haltpoll_enable);
+
+void arch_haltpoll_disable(void)
+{
+ if (!kvm_para_has_feature(KVM_FEATURE_POLL_CONTROL))
+ return;
+
+ preempt_disable();
+ /* Enable guest halt poll disables host halt poll */
+ kvm_enable_host_haltpoll(NULL);
+ smp_call_function(kvm_enable_host_haltpoll, NULL, 1);
+ preempt_enable();
+}
+EXPORT_SYMBOL_GPL(arch_haltpoll_disable);
+#endif