cpuidle-haltpoll: disable host side polling when kvm virtualized

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

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 222855cc0158422f1d6dddc2d9307cb606433a37..05e78acb187c726cd77dc0b979fe84f0aae32d4c 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -794,6 +794,7 @@ 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
@@ -802,6 +803,12 @@ 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---

diff --git a/arch/x86/include/asm/cpuidle_haltpoll.h b/arch/x86/include/asm/cpuidle_haltpoll.h
new file mode 100644 (file)
index 0000000..ff8607d
--- /dev/null
+++ b/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

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index b7f34fe2171e472f7f64bf7f93c9bdfcaefba710..f48401be8ce00a2bb29826e3464df6597ac48ad7 100644 (file)
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -875,3 +875,45 @@ 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

diff --git a/drivers/cpuidle/cpuidle-haltpoll.c b/drivers/cpuidle/cpuidle-haltpoll.c
index 35cfb53e928704082e0c76add9585eb272172e20..9ac093dcbb01f26593b9f989ee6b3faa619fc035 100644 (file)
--- a/drivers/cpuidle/cpuidle-haltpoll.c
+++ b/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_driver = {
 
 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);
 }
 

diff --git a/include/linux/cpuidle_haltpoll.h b/include/linux/cpuidle_haltpoll.h
new file mode 100644 (file)
index 0000000..fe5954c
--- /dev/null
+++ b/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