On Wed, Jul 13, 2022 at 12:28:38PM +0100, Sudip Mukherjee (Codethink) wrote:
> Hi All,
>
> The latest mainline kernel branch fails to build for x86_64 allmodconfig
> with clang and the error is:
>
> 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;
>
>
> git bisect pointed to fc02735b14ff ("KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS")
>
> I will be happy to test any patch or provide any extra log if needed.
I suspect something like this will do.
diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bb05ed4f46bd..6398d39e66b0 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -280,7 +280,7 @@ 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);
