[PATCH v3 2/2] KVM: nVMX: Fix preemption timer bit set in vmcs02 even if L1 doesn't enable it

[Wanpeng Li]

From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

We will go to vcpu_run() loop after L0 emulates VMRESUME which incurs 
kvm_sched_out and kvm_sched_in operations since cond_resched() will be 
called once need resched. Preemption timer will be reprogrammed if vCPU 
is scheduled to a different pCPU. Then the preemption timer bit of vmcs02 
will be set if L0 enable preemption timer to run L1 even if L1 doesn't 
enable preemption timer to run L2.

This patch fix it by don't reprogram preemption timer of vmcs02 if L1's 
vCPU is scheduled on diffent pCPU when we are in the way to vmresume 
nested guest.

Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
Cc: Yunhong Jiang <yunhong.jiang@xxxxxxxxx>
Cc: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
Cc: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
---
 arch/x86/kvm/x86.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0cc6cf8..e8fe16a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2742,7 +2742,8 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 		if (tsc_delta < 0)
 			mark_tsc_unstable("KVM discovered backwards TSC");
 
-		if (kvm_lapic_hv_timer_in_use(vcpu) &&
+		if (!is_guest_mode(vcpu) &&
+			kvm_lapic_hv_timer_in_use(vcpu) &&
 				kvm_x86_ops->set_hv_timer(vcpu,
 					kvm_get_lapic_tscdeadline_msr(vcpu)))
 			kvm_lapic_switch_to_sw_timer(vcpu);
-- 
1.9.1