KVM: in-kernel LAPIC save and restore support
    
    This patch adds a new vcpu-based IOCTL to save and restore the local apic
    registers for a single vcpu. The kernel only copies the apic page as a whole,
    extraction of registers is left to userspace side. On restore, the APIC timer
    is restarted from the initial count, this introduces a little delay, but works
    fine
    
    Signed-off-by: Yaozu (Eddie) Dong <eddie.dong@intel.com>
    Signed-off-by: Qing He <qing.he@intel.com>

---
 drivers/kvm/irq.h      |    1 +
 drivers/kvm/kvm_main.c |   46 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/kvm/lapic.c    |   30 ++++++++++++++++++++++++++++++
 include/linux/kvm.h    |    8 ++++++++
 4 files changed, 85 insertions(+), 0 deletions(-)

diff --git a/drivers/kvm/irq.h b/drivers/kvm/irq.h
index 92e1cfb..44e1fa4 100644
--- a/drivers/kvm/irq.h
+++ b/drivers/kvm/irq.h
@@ -149,6 +149,7 @@ int kvm_apic_match_physical_addr(struct kvm_lapic *apic, u16 dest);
 void kvm_ioapic_update_eoi(struct kvm *kvm, int vector);
 int kvm_apic_match_logical_addr(struct kvm_lapic *apic, u8 mda);
 int kvm_apic_set_irq(struct kvm_lapic *apic, u8 vec, u8 trig);
+void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu);
 int kvm_ioapic_init(struct kvm *kvm);
 void kvm_ioapic_set_irq(struct kvm_ioapic *ioapic, int irq, int level);
 
diff --git a/drivers/kvm/kvm_main.c b/drivers/kvm/kvm_main.c
index 4c66f6d..8fee9bc 100644
--- a/drivers/kvm/kvm_main.c
+++ b/drivers/kvm/kvm_main.c
@@ -2636,6 +2636,27 @@ static int kvm_vcpu_ioctl_set_fpu(struct kvm_vcpu *vcpu, struct kvm_fpu *fpu)
 	return 0;
 }
 
+static int kvm_vcpu_ioctl_get_lapic(struct kvm_vcpu *vcpu,
+				    struct kvm_lapic_state *s)
+{
+	vcpu_load(vcpu);
+	memcpy(s->regs, vcpu->apic->regs, sizeof *s);
+	vcpu_put(vcpu);
+
+	return 0;
+}
+
+static int kvm_vcpu_ioctl_set_lapic(struct kvm_vcpu *vcpu,
+				    struct kvm_lapic_state *s)
+{
+	vcpu_load(vcpu);
+	memcpy(vcpu->apic->regs, s->regs, sizeof *s);
+	kvm_apic_post_state_restore(vcpu);
+	vcpu_put(vcpu);
+
+	return 0;
+}
+
 static long kvm_vcpu_ioctl(struct file *filp,
 			   unsigned int ioctl, unsigned long arg)
 {
@@ -2805,6 +2826,31 @@ static long kvm_vcpu_ioctl(struct file *filp,
 		r = 0;
 		break;
 	}
+	case KVM_GET_LAPIC: {
+		struct kvm_lapic_state lapic;
+
+		memset(&lapic, 0, sizeof lapic);
+		r = kvm_vcpu_ioctl_get_lapic(vcpu, &lapic);
+		if (r)
+			goto out;
+		r = -EFAULT;
+		if (copy_to_user(argp, &lapic, sizeof lapic))
+			goto out;
+		r = 0;
+		break;
+	}
+	case KVM_SET_LAPIC: {
+		struct kvm_lapic_state lapic;
+
+		r = -EFAULT;
+		if (copy_from_user(&lapic, argp, sizeof lapic))
+			goto out;
+		r = kvm_vcpu_ioctl_set_lapic(vcpu, &lapic);;
+		if (r)
+			goto out;
+		r = 0;
+		break;
+	}
 	default:
 		;
 	}
diff --git a/drivers/kvm/lapic.c b/drivers/kvm/lapic.c
index b198434..422e7ea 100644
--- a/drivers/kvm/lapic.c
+++ b/drivers/kvm/lapic.c
@@ -983,3 +983,33 @@ int kvm_get_apic_interrupt(struct kvm_vcpu *vcpu)
 	apic_clear_irr(vector, apic);
 	return vector;
 }
+
+void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu)
+{
+	struct kvm_lapic *apic = vcpu->apic;
+ 	ktime_t now;
+ 	u32 offset, val, tmp;
+ 
+	apic->base_address = vcpu->apic_base &
+			     MSR_IA32_APICBASE_BASE;
+	apic_set_reg(apic, APIC_LVR, APIC_VERSION);
+	val = apic_get_reg(apic, APIC_TMICT);
+	apic_set_reg(apic, APIC_TMCCT, val);
+	apic_update_ppr(apic);
+
+ 	/* TODO: following code can be in a common API */
+	spin_lock_bh(&apic->lock);
+ 	hrtimer_cancel(&apic->timer.dev);
+	apic->timer.pending = 0;
+	val = apic_get_reg(apic, APIC_TDCR);
+	tmp = ((val & 0x3) | ((val & 0x8) >> 1)) + 1;
+	apic->timer.divide_count = 0x1 << (tmp & 0x7);
+ 	now = apic->timer.dev.base->get_time();
+ 	apic->timer.last_update = now;
+	val = apic_get_reg(apic, APIC_TMICT);
+	offset = APIC_BUS_CYCLE_NS * apic->timer.divide_count * val;
+ 	hrtimer_start(&apic->timer.dev,
+ 		      ktime_add_ns(now, offset),
+ 		      HRTIMER_MODE_ABS);
+	spin_unlock_bh(&apic->lock);
+}
diff --git a/include/linux/kvm.h b/include/linux/kvm.h
index 3295a06..6cddf62 100644
--- a/include/linux/kvm.h
+++ b/include/linux/kvm.h
@@ -207,6 +207,12 @@ struct kvm_fpu {
 	__u32 pad2;
 };
 
+/* for KVM_GET_LAPIC and KVM_SET_LAPIC */
+#define KVM_APIC_REG_SIZE 0x400
+struct kvm_lapic_state {
+	char regs[KVM_APIC_REG_SIZE];
+};
+
 struct kvm_segment {
 	__u64 base;
 	__u32 limit;
@@ -379,5 +385,7 @@ struct kvm_signal_mask {
 #define KVM_SET_SIGNAL_MASK       _IOW(KVMIO,  0x8b, struct kvm_signal_mask)
 #define KVM_GET_FPU               _IOR(KVMIO,  0x8c, struct kvm_fpu)
 #define KVM_SET_FPU               _IOW(KVMIO,  0x8d, struct kvm_fpu)
+#define KVM_GET_LAPIC             _IOR(KVMIO,  0x8e, struct kvm_lapic_state)
+#define KVM_SET_LAPIC             _IOW(KVMIO,  0x8f, struct kvm_lapic_state)
 
 #endif