Hi Wei,

I love your patch! Perhaps something to improve:

[auto build test WARNING on tip/x86/core]
[also build test WARNING on asm-generic/master iommu/next tip/timers/core pci/next linus/master v5.10-rc2 next-20201105]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/Wei-Liu/Introducing-Linux-root-partition-support-for-Microsoft-Hypervisor/20201106-010058
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git 238c91115cd05c71447ea071624a4c9fe661f970
config: x86_64-randconfig-s021-20201105 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce:
        # apt-get install sparse
        # sparse version: v0.6.3-76-gf680124b-dirty
        # https://github.com/0day-ci/linux/commit/83c03b4e30e729a77688b8c0ffeffa2a555dcce7
        git remote add linux-review https://github.com/0day-ci/linux
        git fetch --no-tags linux-review Wei-Liu/Introducing-Linux-root-partition-support-for-Microsoft-Hypervisor/20201106-010058
        git checkout 83c03b4e30e729a77688b8c0ffeffa2a555dcce7
        # save the attached .config to linux build tree
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

>> arch/x86/hyperv/hv_init.c:341:13: warning: no previous prototype for 'hv_get_partition_id' [-Wmissing-prototypes]
     341 | void __init hv_get_partition_id(void)
         |             ^~~~~~~~~~~~~~~~~~~

vim +/hv_get_partition_id +341 arch/x86/hyperv/hv_init.c

   340	
 > 341	void __init hv_get_partition_id(void)
   342	{
   343		struct hv_get_partition_id *output_page;
   344		u16 status;
   345		unsigned long flags;
   346	
   347		local_irq_save(flags);
   348		output_page = *this_cpu_ptr(hyperv_pcpu_output_arg);
   349		status = hv_do_hypercall(HVCALL_GET_PARTITION_ID, NULL, output_page) &
   350			HV_HYPERCALL_RESULT_MASK;
   351		if (status != HV_STATUS_SUCCESS)
   352			pr_err("Failed to get partition ID: %d\n", status);
   353		else
   354			hv_current_partition_id = output_page->partition_id;
   355		local_irq_restore(flags);
   356	
   357		/* No point in proceeding if this failed */
   358		BUG_ON(status != HV_STATUS_SUCCESS);
   359	}
   360	

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org