linux-kernel - [PATCH] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl

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Date:   Wed, 13 Jul 2022 08:22:22 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>, x86@...nel.org
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Nathan Chancellor <nathan@...nel.org>, stable@...r.kernel.org,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current

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@...r.kernel.org
Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.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