KVM: nVMX: Migrate the VMX-preemption timer

The hrtimer used to emulate the VMX-preemption timer must be pinned to
the same logical processor as the vCPU thread to be interrupted if we
want to have any hope of adhering to the architectural specification
of the VMX-preemption timer. Even with this change, the emulated
VMX-preemption timer VM-exit occasionally arrives too late.

Signed-off-by: Jim Mattson <[e-mail]>
Reviewed-by: Peter Shier <[e-mail]>
Reviewed-by: Oliver Upton <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

arch/x86/include/asm/kvm_host.h

···
 
 	bool (*apic_init_signal_blocked)(struct kvm_vcpu *vcpu);
 	int (*enable_direct_tlbflush)(struct kvm_vcpu *vcpu);
+
+	void (*migrate_timers)(struct kvm_vcpu *vcpu);
 };
 
 struct kvm_x86_nested_ops {

arch/x86/kvm/irq.c

···
 {
 	__kvm_migrate_apic_timer(vcpu);
 	__kvm_migrate_pit_timer(vcpu);
+	if (kvm_x86_ops.migrate_timers)
+		kvm_x86_ops.migrate_timers(vcpu);
 }
 
 bool kvm_arch_irqfd_allowed(struct kvm *kvm, struct kvm_irqfd *args)

arch/x86/kvm/vmx/vmx.c

···
 	return to_vmx(vcpu)->nested.vmxon;
 }
 
+static void vmx_migrate_timers(struct kvm_vcpu *vcpu)
+{
+	if (is_guest_mode(vcpu)) {
+		struct hrtimer *timer = &to_vmx(vcpu)->nested.preemption_timer;
+
+		if (hrtimer_try_to_cancel(timer) == 1)
+			hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
+	}
+}
+
 static void hardware_unsetup(void)
 {
 	if (nested)
···
 
 	.need_emulation_on_page_fault = vmx_need_emulation_on_page_fault,
 	.apic_init_signal_blocked = vmx_apic_init_signal_blocked,
+	.migrate_timers = vmx_migrate_timers,
 };
 
 static __init int hardware_setup(void)