linux-kernel - Re: [linux-stable-rc:linux-5.10.y 7109/7120] arch/x86/kernel/cpu/bugs.c:57:21: warning: section attribute is specified on redeclared variable

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Message-ID: <Ys3Xu+Vikf9WgIgz@dev-arch.thelio-3990X>
Date:   Tue, 12 Jul 2022 13:21:15 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     kernel test robot <lkp@...el.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>, llvm@...ts.linux.dev,
        kbuild-all@...ts.01.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Borislav Petkov <bp@...e.de>,
        Thadeu Lima de Souza Cascardo <cascardo@...onical.com>,
        Ben Hutchings <bwh@...nel.org>
Subject: Re: [linux-stable-rc:linux-5.10.y 7109/7120]
 arch/x86/kernel/cpu/bugs.c:57:21: warning: section attribute is specified on
 redeclared variable

On Wed, Jul 13, 2022 at 04:07:25AM +0800, kernel test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git linux-5.10.y
> head:   ba398a0e54049bb6a1c102245ae84103f103ff2c
> commit: 855b78ccf1c8c952e148bdbd234cde117b098060 [7109/7120] KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS
> config: i386-randconfig-a013 (https://download.01.org/0day-ci/archive/20220713/202207130344.AUqExE4E-lkp@intel.com/config)
> compiler: clang version 15.0.0 (https://github.com/llvm/llvm-project badda4ac3c489a8c8cccdad1f74b9308c350a9e0)
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git/commit/?id=855b78ccf1c8c952e148bdbd234cde117b098060
>         git remote add linux-stable-rc https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
>         git fetch --no-tags linux-stable-rc linux-5.10.y
>         git checkout 855b78ccf1c8c952e148bdbd234cde117b098060
>         # save the config file
>         mkdir build_dir && cp config build_dir/.config
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash arch/x86/kernel/
> 
> If you fix the issue, kindly add following tag where applicable
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>):
> 
> >> arch/x86/kernel/cpu/bugs.c:57:21: warning: section attribute is specified on redeclared variable [-Wsection]
>    DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
>                        ^
>    arch/x86/include/asm/nospec-branch.h:278:12: note: previous declaration is here
>    extern u64 x86_spec_ctrl_current;
>               ^
>    1 warning generated.
> 
> 
> vim +57 arch/x86/kernel/cpu/bugs.c
> 
> c40221c4c496c5 Peter Zijlstra 2022-06-14  55  
> c40221c4c496c5 Peter Zijlstra 2022-06-14  56  /* The current value of the SPEC_CTRL MSR with task-specific bits set */
> c40221c4c496c5 Peter Zijlstra 2022-06-14 @57  DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
> c40221c4c496c5 Peter Zijlstra 2022-06-14  58  EXPORT_SYMBOL_GPL(x86_spec_ctrl_current);
> c40221c4c496c5 Peter Zijlstra 2022-06-14  59  
> 
> :::::: The code at line 57 was first introduced by commit
> :::::: c40221c4c496c5c026ede111094a96f292875d88 x86/bugs: Keep a per-CPU IA32_SPEC_CTRL value
> 
> :::::: TO: Peter Zijlstra <peterz@...radead.org>
> :::::: CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
> 

Looks like that declaration should be using DECLARE_PER_CPU?

Cheers,
Nathan

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 2989b42fcf4e..cbd56675bd7e 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -281,7 +281,7 @@ static inline void indirect_branch_prediction_barrier(void)
 
 /* The Intel SPEC CTRL MSR base value cache */
 extern u64 x86_spec_ctrl_base;
-extern u64 x86_spec_ctrl_current;
+DECLARE_PER_CPU(u64, x86_spec_ctrl_current);
 extern void write_spec_ctrl_current(u64 val, bool force);
 extern u64 spec_ctrl_current(void);