KVM: PIT support for HPET legacy mode

When kvm is in hpet_legacy_mode, the hpet is providing the timer
interrupt and the pit should not be. So in legacy mode, the pit timer
is destroyed, but the *state* of the pit is maintained. So if kvm or
the guest tries to modify the state of the pit, this modification is
accepted, *except* that the timer isn't actually started. When we exit
hpet_legacy_mode, the current state of the pit (which is up to date
since we've been accepting modifications) is used to restart the pit
timer.

The saved_mode code in kvm_pit_load_count temporarily changes mode to
0xff in order to destroy the timer, but then restores the actual
value, again maintaining "current" state of the pit for possible later
reenablement.

[avi: add some reserved storage in the ioctl; make SET_PIT2 IOW]
[marcelo: fix memory corruption due to reserved storage]

Signed-off-by: Beth Kon <eak@us.ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 58 insertions, 1 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dfb0e37..2214384 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1213,6 +1213,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	case KVM_CAP_ASSIGN_DEV_IRQ:
 	case KVM_CAP_IRQFD:
 	case KVM_CAP_PIT2:
+	case KVM_CAP_PIT_STATE2:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -2078,7 +2079,36 @@ static int kvm_vm_ioctl_set_pit(struct kvm *kvm, struct kvm_pit_state *ps)
 
 	mutex_lock(&kvm->arch.vpit->pit_state.lock);
 	memcpy(&kvm->arch.vpit->pit_state, ps, sizeof(struct kvm_pit_state));
-	kvm_pit_load_count(kvm, 0, ps->channels[0].count);
+	kvm_pit_load_count(kvm, 0, ps->channels[0].count, 0);
+	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+	return r;
+}
+
+static int kvm_vm_ioctl_get_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
+{
+	int r = 0;
+
+	mutex_lock(&kvm->arch.vpit->pit_state.lock);
+	memcpy(ps->channels, &kvm->arch.vpit->pit_state.channels,
+		sizeof(ps->channels));
+	ps->flags = kvm->arch.vpit->pit_state.flags;
+	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
+	return r;
+}
+
+static int kvm_vm_ioctl_set_pit2(struct kvm *kvm, struct kvm_pit_state2 *ps)
+{
+	int r = 0, start = 0;
+	u32 prev_legacy, cur_legacy;
+	mutex_lock(&kvm->arch.vpit->pit_state.lock);
+	prev_legacy = kvm->arch.vpit->pit_state.flags & KVM_PIT_FLAGS_HPET_LEGACY;
+	cur_legacy = ps->flags & KVM_PIT_FLAGS_HPET_LEGACY;
+	if (!prev_legacy && cur_legacy)
+		start = 1;
+	memcpy(&kvm->arch.vpit->pit_state.channels, &ps->channels,
+	       sizeof(kvm->arch.vpit->pit_state.channels));
+	kvm->arch.vpit->pit_state.flags = ps->flags;
+	kvm_pit_load_count(kvm, 0, kvm->arch.vpit->pit_state.channels[0].count, start);
 	mutex_unlock(&kvm->arch.vpit->pit_state.lock);
 	return r;
 }
@@ -2140,6 +2170,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
 	 */
 	union {
 		struct kvm_pit_state ps;
+		struct kvm_pit_state2 ps2;
 		struct kvm_memory_alias alias;
 		struct kvm_pit_config pit_config;
 	} u;
@@ -2322,6 +2353,32 @@ long kvm_arch_vm_ioctl(struct file *filp,
 		r = 0;
 		break;
 	}
+	case KVM_GET_PIT2: {
+		r = -ENXIO;
+		if (!kvm->arch.vpit)
+			goto out;
+		r = kvm_vm_ioctl_get_pit2(kvm, &u.ps2);
+		if (r)
+			goto out;
+		r = -EFAULT;
+		if (copy_to_user(argp, &u.ps2, sizeof(u.ps2)))
+			goto out;
+		r = 0;
+		break;
+	}
+	case KVM_SET_PIT2: {
+		r = -EFAULT;
+		if (copy_from_user(&u.ps2, argp, sizeof(u.ps2)))
+			goto out;
+		r = -ENXIO;
+		if (!kvm->arch.vpit)
+			goto out;
+		r = kvm_vm_ioctl_set_pit2(kvm, &u.ps2);
+		if (r)
+			goto out;
+		r = 0;
+		break;
+	}
 	case KVM_REINJECT_CONTROL: {
 		struct kvm_reinject_control control;
 		r =  -EFAULT;