linux-kernel - Re: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests

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Message-ID: <202602052054.J3CEkmKB-lkp@intel.com>
Date: Thu, 5 Feb 2026 20:35:25 +0800
From: kernel test robot <lkp@...el.com>
To: Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, bp@...en8.de, thomas.lendacky@....com
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev, tglx@...nel.org,
	mingo@...hat.com, dave.hansen@...ux.intel.com, hpa@...or.com,
	xin@...or.com, seanjc@...gle.com, pbonzini@...hat.com,
	x86@...nel.org, jon.grimm@....com, nikunj@....com,
	stable@...r.kernel.org
Subject: Re: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests

Hi Nikunj,

kernel test robot noticed the following build errors:

[auto build test ERROR on 3c2ca964f75460093a8aad6b314a6cd558e80e66]

url:    https://github.com/intel-lab-lkp/linux/commits/Nikunj-A-Dadhania/x86-fred-Fix-early-boot-failures-on-SEV-ES-SNP-guests/20260205-131359
base:   3c2ca964f75460093a8aad6b314a6cd558e80e66
patch link:    https://lore.kernel.org/r/20260205051030.1225975-1-nikunj%40amd.com
patch subject: [PATCH] x86/fred: Fix early boot failures on SEV-ES/SNP guests
config: x86_64-kexec (https://download.01.org/0day-ci/archive/20260205/202602052054.J3CEkmKB-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260205/202602052054.J3CEkmKB-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602052054.J3CEkmKB-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/x86/entry/entry_fred.c:213:11: error: call to undeclared function 'user_exc_vmm_communication'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     213 |                         return user_exc_vmm_communication(regs, error_code);
         |                                ^
   arch/x86/entry/entry_fred.c:213:4: warning: void function 'fred_hwexc' should not return a value [-Wreturn-mismatch]
     213 |                         return user_exc_vmm_communication(regs, error_code);
         |                         ^      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> arch/x86/entry/entry_fred.c:215:11: error: call to undeclared function 'kernel_exc_vmm_communication'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
     215 |                         return kernel_exc_vmm_communication(regs, error_code);
         |                                ^
   arch/x86/entry/entry_fred.c:215:4: warning: void function 'fred_hwexc' should not return a value [-Wreturn-mismatch]
     215 |                         return kernel_exc_vmm_communication(regs, error_code);
         |                         ^      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   2 warnings and 2 errors generated.


vim +/user_exc_vmm_communication +213 arch/x86/entry/entry_fred.c

   180	
   181	static noinstr void fred_hwexc(struct pt_regs *regs, unsigned long error_code)
   182	{
   183		/* Optimize for #PF. That's the only exception which matters performance wise */
   184		if (likely(regs->fred_ss.vector == X86_TRAP_PF))
   185			return exc_page_fault(regs, error_code);
   186	
   187		switch (regs->fred_ss.vector) {
   188		case X86_TRAP_DE: return exc_divide_error(regs);
   189		case X86_TRAP_DB: return fred_exc_debug(regs);
   190		case X86_TRAP_BR: return exc_bounds(regs);
   191		case X86_TRAP_UD: return exc_invalid_op(regs);
   192		case X86_TRAP_NM: return exc_device_not_available(regs);
   193		case X86_TRAP_DF: return exc_double_fault(regs, error_code);
   194		case X86_TRAP_TS: return exc_invalid_tss(regs, error_code);
   195		case X86_TRAP_NP: return exc_segment_not_present(regs, error_code);
   196		case X86_TRAP_SS: return exc_stack_segment(regs, error_code);
   197		case X86_TRAP_GP: return exc_general_protection(regs, error_code);
   198		case X86_TRAP_MF: return exc_coprocessor_error(regs);
   199		case X86_TRAP_AC: return exc_alignment_check(regs, error_code);
   200		case X86_TRAP_XF: return exc_simd_coprocessor_error(regs);
   201	
   202	#ifdef CONFIG_X86_MCE
   203		case X86_TRAP_MC: return fred_exc_machine_check(regs);
   204	#endif
   205	#ifdef CONFIG_INTEL_TDX_GUEST
   206		case X86_TRAP_VE: return exc_virtualization_exception(regs);
   207	#endif
   208	#ifdef CONFIG_X86_CET
   209		case X86_TRAP_CP: return exc_control_protection(regs, error_code);
   210	#endif
   211		case X86_TRAP_VC:
   212			if (user_mode(regs))
 > 213				return user_exc_vmm_communication(regs, error_code);
   214			else
 > 215				return kernel_exc_vmm_communication(regs, error_code);
   216		default: return fred_bad_type(regs, error_code);
   217		}
   218	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki