2022-07-13 15:36:30

by Nathan Chancellor

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: [email protected]
Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Nathan Chancellor <[email protected]>
---
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

2022-07-13 15:37:49

by Nathan Chancellor

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

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: [email protected]
> Fixes: fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: Nathan Chancellor <[email protected]>
> ---
> 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
>