tree:   https://github.com/intel/tdx.git guest
head:   c748712bd17bbd7f8a75553911a5557f3d7d32b2
commit: b050815868ea9723b6b08badd2bbb887fdbc454c [19/127] x86/tdx: Wire up KVM hypercalls
config: i386-tinyconfig (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel/tdx/commit/b050815868ea9723b6b08badd2bbb887fdbc454c
        git remote add intel-tdx https://github.com/intel/tdx.git
        git fetch --no-tags intel-tdx guest
        git checkout b050815868ea9723b6b08badd2bbb887fdbc454c
        # save the attached .config to linux build tree
        make W=1 ARCH=i386 

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

All errors (new ones prefixed by >>):

   In file included from arch/x86/mm/fault.c:33:
   arch/x86/include/asm/kvm_para.h: In function 'kvm_hypercall0':
>> arch/x86/include/asm/kvm_para.h:39:10: error: implicit declaration of function 'tdx_kvm_hypercall'; did you mean 'kvm_hypercall0'? [-Werror=implicit-function-declaration]
      39 |   return tdx_kvm_hypercall(nr, 0, 0, 0, 0);
         |          ^~~~~~~~~~~~~~~~~
         |          kvm_hypercall0
   cc1: some warnings being treated as errors


vim +39 arch/x86/include/asm/kvm_para.h

    20	
    21	#define KVM_HYPERCALL \
    22	        ALTERNATIVE("vmcall", "vmmcall", X86_FEATURE_VMMCALL)
    23	
    24	/* For KVM hypercalls, a three-byte sequence of either the vmcall or the vmmcall
    25	 * instruction.  The hypervisor may replace it with something else but only the
    26	 * instructions are guaranteed to be supported.
    27	 *
    28	 * Up to four arguments may be passed in rbx, rcx, rdx, and rsi respectively.
    29	 * The hypercall number should be placed in rax and the return value will be
    30	 * placed in rax.  No other registers will be clobbered unless explicitly
    31	 * noted by the particular hypercall.
    32	 */
    33	
    34	static inline long kvm_hypercall0(unsigned int nr)
    35	{
    36		long ret;
    37	
    38		if (prot_guest_has(PATTR_GUEST_TDX))
  > 39			return tdx_kvm_hypercall(nr, 0, 0, 0, 0);
    40	
    41		asm volatile(KVM_HYPERCALL
    42			     : "=a"(ret)
    43			     : "a"(nr)
    44			     : "memory");
    45		return ret;
    46	}
    47	

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