[PATCH v3 1/3] KVM: LAPIC: Fix lapic timer mode transition

[Wanpeng Li <kernellwp@gmail.com>]

From: Wanpeng Li <wanpeng.li@hotmail.com>

SDM 10.5.4.1 TSC-Deadline Mode mentioned that "Transitioning between TSC-Deadline
mode and other timer modes also disarms the timer". So the APIC Timer Initial Count
Register for one-shot/periodic mode should be reset. This patch do it.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
 arch/x86/include/asm/apicdef.h | 1 +
 arch/x86/kvm/lapic.c           | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/apicdef.h b/arch/x86/include/asm/apicdef.h
index c46bb99..7fde8e9 100644
--- a/arch/x86/include/asm/apicdef.h
+++ b/arch/x86/include/asm/apicdef.h
@@ -100,6 +100,7 @@
 #define		APIC_TIMER_BASE_CLKIN		0x0
 #define		APIC_TIMER_BASE_TMBASE		0x1
 #define		APIC_TIMER_BASE_DIV		0x2
+#define		APIC_LVT_TIMER_MASK		(3 << 17)
 #define		APIC_LVT_TIMER_ONESHOT		(0 << 17)
 #define		APIC_LVT_TIMER_PERIODIC		(1 << 17)
 #define		APIC_LVT_TIMER_TSCDEADLINE	(2 << 17)
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 69c5612..6723e2c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1307,6 +1307,9 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
 			apic->lapic_timer.timer_mode_mask;
 
 	if (apic->lapic_timer.timer_mode != timer_mode) {
+		if (apic_lvtt_tscdeadline(apic) != (timer_mode ==
+				APIC_LVT_TIMER_TSCDEADLINE))
+			kvm_lapic_set_reg(apic, APIC_TMICT, 0);
 		apic->lapic_timer.timer_mode = timer_mode;
 		hrtimer_cancel(&apic->lapic_timer.timer);
 	}
-- 
2.7.4