[PATCH] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current

[PATCH] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current

[Nathan Chancellor]

Clang warns:

  arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
  DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
                      ^
  arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
  extern u64 x86_spec_ctrl_current;
             ^
  1 error generated.

The declaration should be using DECLARE_PER_CPU instead so all
attributes stay in sync.

Cc: stable@vger.kernel.org
Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/x86/include/asm/nospec-branch.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bb05ed4f46bd..99a29c83adf8 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -6,6 +6,7 @@
 #include <linux/static_key.h>
 #include <linux/objtool.h>
 #include <linux/linkage.h>
+#include <linux/percpu.h>
 
 #include <asm/alternative.h>
 #include <asm/cpufeatures.h>
@@ -280,7 +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);
 

base-commit: 72a8e05d4f66b5af7854df4490e3135168694b6b
-- 
2.37.1

Re: [PATCH] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current

[Nathan Chancellor]

On Wed, Jul 13, 2022 at 08:22:22AM -0700, Nathan Chancellor wrote:
> Clang warns:
> 
>   arch/x86/kernel/cpu/bugs.c:58:21: error: section attribute is specified on redeclared variable [-Werror,-Wsection]
>   DEFINE_PER_CPU(u64, x86_spec_ctrl_current);
>                       ^
>   arch/x86/include/asm/nospec-branch.h:283:12: note: previous declaration is here
>   extern u64 x86_spec_ctrl_current;
>              ^
>   1 error generated.
> 
> The declaration should be using DECLARE_PER_CPU instead so all
> attributes stay in sync.
> 
> Cc: stable@vger.kernel.org
> Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
> Reported-by: kernel test robot <lkp@intel.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  arch/x86/include/asm/nospec-branch.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
> index bb05ed4f46bd..99a29c83adf8 100644
> --- a/arch/x86/include/asm/nospec-branch.h
> +++ b/arch/x86/include/asm/nospec-branch.h
> @@ -6,6 +6,7 @@
>  #include <linux/static_key.h>
>  #include <linux/objtool.h>
>  #include <linux/linkage.h>
> +#include <linux/percpu.h>

Argh, forgot to amend... v2 incoming.

>  #include <asm/alternative.h>
>  #include <asm/cpufeatures.h>
> @@ -280,7 +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);
>  
> 
> base-commit: 72a8e05d4f66b5af7854df4490e3135168694b6b
> -- 
> 2.37.1
>