kvm: x86: implement KVM PM-notifier

Implement PM hibernation/suspend prepare notifiers so that KVM
can reliably set PVCLOCK_GUEST_STOPPED on VCPUs and properly
suspend VMs.
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Message-Id: <20210606021045.14159-2-senozhatsky@chromium.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/Kconfig

@@ -46,6 +46,7 @@ config KVM
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_VFIO
 	select SRCU
+	select HAVE_KVM_PM_NOTIFIER if PM
 	help
 	  Support hosting fully virtualized guest machines using hardware
 	  virtualization extensions.  You will need a fairly recent

arch/x86/kvm/x86.c

@@ -58,6 +58,7 @@
 #include <linux/sched/isolation.h>
 #include <linux/mem_encrypt.h>
 #include <linux/entry-kvm.h>
+#include <linux/suspend.h>
 
 #include <trace/events/kvm.h>
 
@@ -5701,6 +5702,41 @@ static int kvm_vm_ioctl_set_msr_filter(struct kvm *kvm, void __user *argp)
 	return 0;
 }
 
+#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
+static int kvm_arch_suspend_notifier(struct kvm *kvm)
+{
+	struct kvm_vcpu *vcpu;
+	int i, ret = 0;
+
+	mutex_lock(&kvm->lock);
+	kvm_for_each_vcpu(i, vcpu, kvm) {
+		if (!vcpu->arch.pv_time_enabled)
+			continue;
+
+		ret = kvm_set_guest_paused(vcpu);
+		if (ret) {
+			kvm_err("Failed to pause guest VCPU%d: %d\n",
+				vcpu->vcpu_id, ret);
+			break;
+		}
+	}
+	mutex_unlock(&kvm->lock);
+
+	return ret ? NOTIFY_BAD : NOTIFY_DONE;
+}
+
+int kvm_arch_pm_notifier(struct kvm *kvm, unsigned long state)
+{
+	switch (state) {
+	case PM_HIBERNATION_PREPARE:
+	case PM_SUSPEND_PREPARE:
+		return kvm_arch_suspend_notifier(kvm);
+	}
+
+	return NOTIFY_DONE;
+}
+#endif /* CONFIG_HAVE_KVM_PM_NOTIFIER */
+
 long kvm_arch_vm_ioctl(struct file *filp,
 		       unsigned int ioctl, unsigned long arg)
 {