Hi Wanpeng,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on kvm/linux-next]
[also build test ERROR on v4.18-rc2 next-20180629]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Wanpeng-Li/KVM-x86-Add-PV-IPIs-support/20180629-185314
base:   https://git.kernel.org/pub/scm/virt/kvm/kvm.git linux-next
config: i386-randconfig-a0-201825 (attached as .config)
compiler: gcc-4.9 (Debian 4.9.4-2) 4.9.4
reproduce:
        # save the attached .config to linux build tree
        make ARCH=i386 

All errors (new ones prefixed by >>):

   arch/x86//kernel/kvm.c: In function 'kvm_apic_init':
>> arch/x86//kernel/kvm.c:681:3: error: implicit declaration of function 'kvm_setup_pv_ipi' [-Werror=implicit-function-declaration]
      kvm_setup_pv_ipi();
      ^
   cc1: some warnings being treated as errors

vim +/kvm_setup_pv_ipi +681 arch/x86//kernel/kvm.c

   677	
   678	static void __init kvm_apic_init(void)
   679	{
   680		if (kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI))
 > 681			kvm_setup_pv_ipi();
   682	}
   683	

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