From 8d63399e79b6aeec974dfaa92db48307f8629e61 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Tue, 30 Dec 2008 17:55:06 -0200
Subject: [PATCH 4/9] KVM: PIT: provide an option to disable interrupt reinjection

Certain clocks (such as TSC) in older 2.6 guests overaccount for lost
ticks, causing severe time drift. Interrupt reinjection magnifies the
problem.

Provide an option to disable it.

[avi: allow room for expansion in case we want to disable reinjection
      of other timers]
[ehabkost: comment KVM_CAP_SET_GUEST_DEBUG definition to avoid breaking
      userspace code]

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
RH-Type: bugfix
RH-Upstream-status: applied(kvm/master),pending(maint/2.6.29)
---
 arch/x86/include/asm/kvm.h |    5 +++++
 arch/x86/kvm/i8254.c       |    4 ++++
 arch/x86/kvm/i8254.h       |    1 +
 arch/x86/kvm/x86.c         |   21 +++++++++++++++++++++
 include/linux/kvm.h        |    5 +++++
 5 files changed, 36 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/kvm.h b/arch/x86/include/asm/kvm.h
index b95162a..cf24d4b 100644
--- a/arch/x86/include/asm/kvm.h
+++ b/arch/x86/include/asm/kvm.h
@@ -208,4 +208,9 @@ struct kvm_pit_channel_state {
 struct kvm_pit_state {
 	struct kvm_pit_channel_state channels[3];
 };
+
+struct kvm_reinject_control {
+	__u8 pit_reinject;
+	__u8 reserved[31];
+};
 #endif /* _ASM_X86_KVM_H */
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 72bd275..528daad 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -201,6 +201,9 @@ static int __pit_timer_fn(struct kvm_kpit_state *ps)
 	if (!atomic_inc_and_test(&pt->pending))
 		set_bit(KVM_REQ_PENDING_TIMER, &vcpu0->requests);
 
+	if (!pt->reinject)
+		atomic_set(&pt->pending, 1);
+
 	if (vcpu0 && waitqueue_active(&vcpu0->wq))
 		wake_up_interruptible(&vcpu0->wq);
 
@@ -580,6 +583,7 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm)
 	pit_state->irq_ack_notifier.gsi = 0;
 	pit_state->irq_ack_notifier.irq_acked = kvm_pit_ack_irq;
 	kvm_register_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier);
+	pit_state->pit_timer.reinject = true;
 	mutex_unlock(&pit->pit_state.lock);
 
 	kvm_pit_reset(pit);
diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
index 4178022..76959c4 100644
--- a/arch/x86/kvm/i8254.h
+++ b/arch/x86/kvm/i8254.h
@@ -9,6 +9,7 @@ struct kvm_kpit_timer {
 	s64 period; /* unit: ns */
 	s64 scheduled;
 	atomic_t pending;
+	bool reinject;
 };
 
 struct kvm_kpit_channel_state {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index cc17546..79b5181 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -972,6 +972,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_NOP_IO_DELAY:
 	case KVM_CAP_MP_STATE:
 	case KVM_CAP_SYNC_MMU:
+	case KVM_CAP_REINJECT_CONTROL:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -1708,6 +1709,15 @@ static int kvm_vm_ioctl_set_pit(struct kvm *kvm, struct kvm_pit_state *ps)
 	return r;
 }
 
+static int kvm_vm_ioctl_reinject(struct kvm *kvm,
+				 struct kvm_reinject_control *control)
+{
+	if (!kvm->arch.vpit)
+		return -ENXIO;
+	kvm->arch.vpit->pit_state.pit_timer.reinject = control->pit_reinject;
+	return 0;
+}
+
 /*
  * Get (and clear) the dirty memory log for a memory slot.
  */
@@ -1905,6 +1915,17 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = 0;
 		break;
 	}
+	case KVM_REINJECT_CONTROL: {
+		struct kvm_reinject_control control;
+		r =  -EFAULT;
+		if (copy_from_user(&control, argp, sizeof(control)))
+			goto out;
+		r = kvm_vm_ioctl_reinject(kvm, &control);
+		if (r)
+			goto out;
+		r = 0;
+		break;
+	}
 	default:
 		;
 	}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 35525ac..f077b2b 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -396,6 +396,10 @@ struct kvm_trace_rec {
 #if defined(CONFIG_X86)
 #define KVM_CAP_USER_NMI 22
 #endif
+//#define KVM_CAP_SET_GUEST_DEBUG 23
+#if defined(CONFIG_X86)
+#define KVM_CAP_REINJECT_CONTROL 24
+#endif
 
 /*
  * ioctls for VM fds
@@ -429,6 +433,7 @@ struct kvm_trace_rec {
 				   struct kvm_assigned_pci_dev)
 #define KVM_ASSIGN_IRQ _IOR(KVMIO, 0x70, \
 			    struct kvm_assigned_irq)
+#define KVM_REINJECT_CONTROL      _IO(KVMIO, 0x71)
 
 /*
  * ioctls for vcpu fds
-- 
1.6.1