[PATCH v2 1/4] KVM: LAPIC: Fix lapic timer mode transition

From	Wanpeng Li <kernellwp@gmail.com>
Newsgroups	linux.kernel
Subject	[PATCH v2 1/4] KVM: LAPIC: Fix lapic timer mode transition
Date	2017-09-29 03:10 +0200
Message-ID	<uuRYu-7Tm-5@gated-at.bofh.it> (permalink)
References	<uuRYu-7Tm-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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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..d8ef1b4 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..a739cbb 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1722,6 +1722,9 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 		break;
 
 	case APIC_LVTT:
+		if (apic_lvtt_tscdeadline(apic) != ((val &
+			APIC_LVT_TIMER_MASK) == APIC_LVT_TIMER_TSCDEADLINE))
+			kvm_lapic_set_reg(apic, APIC_TMICT, 0);
 		if (!kvm_apic_sw_enabled(apic))
 			val |= APIC_LVT_MASKED;
 		val &= (apic_lvt_mask[0] | apic->lapic_timer.timer_mode_mask);
-- 
2.7.4

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[PATCH v2 1/4] KVM: LAPIC: Fix lapic timer mode transition Wanpeng Li <kernellwp@gmail.com> - 2017-09-29 03:10 +0200

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