linux-kernel - Re: [PATCH v2] KVM: x86: Unify L1TF flushing under per-CPU variable

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Message-ID: <202510161648.7Ere0Lfz-lkp@intel.com>
Date: Thu, 16 Oct 2025 16:59:42 +0800
From: kernel test robot <lkp@...el.com>
To: Brendan Jackman <jackmanb@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	Brendan Jackman <jackmanb@...gle.com>
Subject: Re: [PATCH v2] KVM: x86: Unify L1TF flushing under per-CPU variable

Hi Brendan,

kernel test robot noticed the following build errors:

[auto build test ERROR on 6b36119b94d0b2bb8cea9d512017efafd461d6ac]

url:    https://github.com/intel-lab-lkp/linux/commits/Brendan-Jackman/KVM-x86-Unify-L1TF-flushing-under-per-CPU-variable/20251016-011539
base:   6b36119b94d0b2bb8cea9d512017efafd461d6ac
patch link:    https://lore.kernel.org/r/20251015-b4-l1tf-percpu-v2-1-6d7a8d3d40e9%40google.com
patch subject: [PATCH v2] KVM: x86: Unify L1TF flushing under per-CPU variable
config: i386-buildonly-randconfig-005-20251016 (https://download.01.org/0day-ci/archive/20251016/202510161648.7Ere0Lfz-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/20251016/202510161648.7Ere0Lfz-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/202510161648.7Ere0Lfz-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/x86/kvm/x86.c:8003:2: error: call to undeclared function 'kvm_set_cpu_l1tf_flush_l1d_raw'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    8003 |         kvm_set_cpu_l1tf_flush_l1d_raw();
         |         ^
   arch/x86/kvm/x86.c:8003:2: note: did you mean 'kvm_set_cpu_l1tf_flush_l1d'?
   arch/x86/include/asm/hardirq.h:97:29: note: 'kvm_set_cpu_l1tf_flush_l1d' declared here
      97 | static __always_inline void kvm_set_cpu_l1tf_flush_l1d(void) { }
         |                             ^
   arch/x86/kvm/x86.c:9399:2: error: call to undeclared function 'kvm_set_cpu_l1tf_flush_l1d_raw'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
    9399 |         kvm_set_cpu_l1tf_flush_l1d_raw();
         |         ^
   2 errors generated.


vim +/kvm_set_cpu_l1tf_flush_l1d_raw +8003 arch/x86/kvm/x86.c

  7998	
  7999	int kvm_write_guest_virt_system(struct kvm_vcpu *vcpu, gva_t addr, void *val,
  8000					unsigned int bytes, struct x86_exception *exception)
  8001	{
  8002		/* kvm_write_guest_virt_system can pull in tons of pages. */
> 8003		kvm_set_cpu_l1tf_flush_l1d_raw();
  8004	
  8005		return kvm_write_guest_virt_helper(addr, val, bytes, vcpu,
  8006						   PFERR_WRITE_MASK, exception);
  8007	}
  8008	EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_write_guest_virt_system);
  8009	

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