Hi Srinivasan,

I love your patch! Yet something to improve:

[auto build test ERROR on v4.17-rc3]
[also build test ERROR on next-20180504]
[cannot apply to tip/x86/core]
[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/kys-linuxonhyperv-com/X86-Hyper-V-APIC-enlightenments/20180505-045627
config: x86_64-randconfig-a0-05050447 (attached as .config)
compiler: gcc-7 (Debian 7.3.0-16) 7.3.0
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

All errors (new ones prefixed by >>):

   arch/x86/hyperv/hv_apic.c: In function 'hv_apic_read':
>> arch/x86/hyperv/hv_apic.c:66:10: error: implicit declaration of function 'native_apic_mem_read'; did you mean 'hv_apic_icr_read'? [-Werror=implicit-function-declaration]
      return native_apic_mem_read(reg);
             ^~~~~~~~~~~~~~~~~~~~
             hv_apic_icr_read
   arch/x86/hyperv/hv_apic.c: In function 'hv_apic_write':
>> arch/x86/hyperv/hv_apic.c:80:3: error: implicit declaration of function 'native_apic_mem_write'; did you mean 'hv_apic_icr_write'? [-Werror=implicit-function-declaration]
      native_apic_mem_write(reg, val);
      ^~~~~~~~~~~~~~~~~~~~~
      hv_apic_icr_write
   arch/x86/hyperv/hv_apic.c: In function 'hv_apic_init':
>> arch/x86/hyperv/hv_apic.c:93:3: error: implicit declaration of function 'apic_set_eoi_write'; did you mean 'hv_apic_eoi_write'? [-Werror=implicit-function-declaration]
      apic_set_eoi_write(hv_apic_eoi_write);
      ^~~~~~~~~~~~~~~~~~
      hv_apic_eoi_write
   arch/x86/hyperv/hv_apic.c:94:3: error: 'apic' undeclared (first use in this function); did you mean 'pid'?
      apic->read      = hv_apic_read;
      ^~~~
      pid
   arch/x86/hyperv/hv_apic.c:94:3: note: each undeclared identifier is reported only once for each function it appears in
   cc1: some warnings being treated as errors

vim +66 arch/x86/hyperv/hv_apic.c

    52	
    53	static u32 hv_apic_read(u32 reg)
    54	{
    55		u32 reg_val, hi;
    56	
    57		switch (reg) {
    58		case APIC_EOI:
    59			rdmsr(HV_X64_MSR_EOI, reg_val, hi);
    60			return reg_val;
    61		case APIC_TASKPRI:
    62			rdmsr(HV_X64_MSR_TPR, reg_val, hi);
    63			return reg_val;
    64	
    65		default:
  > 66			return native_apic_mem_read(reg);
    67		}
    68	}
    69	
    70	static void hv_apic_write(u32 reg, u32 val)
    71	{
    72		switch (reg) {
    73		case APIC_EOI:
    74			wrmsr(HV_X64_MSR_EOI, val, 0);
    75			break;
    76		case APIC_TASKPRI:
    77			wrmsr(HV_X64_MSR_TPR, val, 0);
    78			break;
    79		default:
  > 80			native_apic_mem_write(reg, val);
    81		}
    82	}
    83	
    84	static void hv_apic_eoi_write(u32 reg, u32 val)
    85	{
    86		wrmsr(HV_X64_MSR_EOI, val, 0);
    87	}
    88	
    89	void __init hv_apic_init(void)
    90	{
    91		if (ms_hyperv.hints & HV_X64_APIC_ACCESS_RECOMMENDED) {
    92			pr_info("Hyper-V: Using MSR based APIC access\n");
  > 93			apic_set_eoi_write(hv_apic_eoi_write);
    94			apic->read      = hv_apic_read;
    95			apic->write     = hv_apic_write;
    96			apic->icr_write = hv_apic_icr_write;
    97			apic->icr_read  = hv_apic_icr_read;
    98		}
    99	}
   100	

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