[linux-next:master 9088/11791] drivers/virt/acrn/hsm.c:389:3: error: implicit declaration of function 'remove_cpu'

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
head:   ff90dfd2579b2c7bc1f0baa0cb99c918c6c1ec64
commit: 279dcf693ac76c9d16b91ffc41280babaff26bb2 [9088/11791] virt: acrn: Introduce an interface for Service VM to control vCPU
config: x86_64-randconfig-r031-20210218 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0
reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=279dcf693ac76c9d16b91ffc41280babaff26bb2
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout 279dcf693ac76c9d16b91ffc41280babaff26bb2
        # save the attached .config to linux build tree
        make W=1 ARCH=x86_64 

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <redacted>

All errors (new ones prefixed by >>):

   drivers/virt/acrn/hsm.c: In function 'remove_cpu_store':

quoted

drivers/virt/acrn/hsm.c:389:3: error: implicit declaration of function 'remove_cpu' [-Werror=implicit-function-declaration]

     389 |   remove_cpu(cpu);
         |   ^~~~~~~~~~

quoted

drivers/virt/acrn/hsm.c:402:2: error: implicit declaration of function 'add_cpu' [-Werror=implicit-function-declaration]

     402 |  add_cpu(cpu);
         |  ^~~~~~~
   cc1: some warnings being treated as errors


vim +/remove_cpu +389 drivers/virt/acrn/hsm.c

   374	
   375	static ssize_t remove_cpu_store(struct device *dev,
   376					struct device_attribute *attr,
   377					const char *buf, size_t count)
   378	{
   379		u64 cpu, lapicid;
   380		int ret;
   381	
   382		if (kstrtoull(buf, 0, &cpu) < 0)
   383			return -EINVAL;
   384	
   385		if (cpu >= num_possible_cpus() || cpu == 0 || !cpu_is_hotpluggable(cpu))
   386			return -EINVAL;
   387	
   388		if (cpu_online(cpu))
 > 389			remove_cpu(cpu);
   390	
   391		lapicid = cpu_data(cpu).apicid;
   392		dev_dbg(dev, "Try to remove cpu %lld with lapicid %lld\n", cpu, lapicid);
   393		ret = hcall_sos_remove_cpu(lapicid);
   394		if (ret < 0) {
   395			dev_err(dev, "Failed to remove cpu %lld!\n", cpu);
   396			goto fail_remove;
   397		}
   398	
   399		return count;
   400	
   401	fail_remove:
 > 402		add_cpu(cpu);
   403		return ret;
   404	}
   405	static DEVICE_ATTR_WO(remove_cpu);
   406	

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