[PATCH v2] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current

From: Nathan Chancellor <nathan@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>, x86@kernel.org
Cc: Nick Desaulniers <ndesaulniers@google.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Josh Poimboeuf <jpoimboe@kernel.org>,
	linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
	Nathan Chancellor <nathan@kernel.org>,
	stable@vger.kernel.org, kernel test robot <lkp@intel.com>
Subject: [PATCH v2] x86/speculation: Use DECLARE_PER_CPU for x86_spec_ctrl_current
Date: Wed, 13 Jul 2022 08:24:37 -0700	[thread overview]
Message-ID: <20220713152436.2294819-1-nathan@kernel.org> (raw)

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>
---

v1 -> v2: https://lore.kernel.org/20220713152222.1697913-1-nathan@kernel.org/

* Use asm/percpu.h instead of linux/percpu.h to avoid static call
  include errors.

 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..10a3bfc1eb23 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -11,6 +11,7 @@
 #include <asm/cpufeatures.h>
 #include <asm/msr-index.h>
 #include <asm/unwind_hints.h>
+#include <asm/percpu.h>
 
 #define RETPOLINE_THUNK_SIZE	32
 
@@ -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

