linux-kernel - [PATCH] [v2] x86: Fix amd_check

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Date:   Tue, 25 Jul 2023 14:17:39 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org
Cc:     Arnd Bergmann <arnd@...db.de>, "H. Peter Anvin" <hpa@...or.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Brian Gerst <brgerst@...il.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] [v2] x86: Fix amd_check_microcode() declaration

From: Arnd Bergmann <arnd@...db.de>

The newly added amd_check_microcode() function has two conflicting definitions
if CONFIG_CPU_SUP_AMD is enabled and CONFIG_MICROCODE_AMD is disabled. Since
the header with the stub definition is not included in cpu/amd.c, this only
causes a -Wmissing-prototype warning with W=1

arch/x86/kernel/cpu/amd.c:1289:6: error: no previous prototype for 'amd_check_microcode' [-Werror=missing-prototypes]

Adding the missing #include shows the other problem:

arch/x86/kernel/cpu/amd.c:1290:6: error: redefinition of 'amd_check_microcode'
arch/x86/include/asm/microcode_amd.h:58:20: note: previous definition of 'amd_check_microcode' with type 'void(void)'

Move the declaration into a more appropriate header that is already included,
with the #ifdef check changed to match the definition's.

Fixes: 522b1d69219d8 ("x86/cpu/amd: Add a Zenbleed fix")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/x86/include/asm/microcode_amd.h | 3 +--
 arch/x86/include/asm/processor.h     | 2 ++
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/microcode_amd.h b/arch/x86/include/asm/microcode_amd.h
index 9675c621c1ca4..2ed09a1da4a27 100644
--- a/arch/x86/include/asm/microcode_amd.h
+++ b/arch/x86/include/asm/microcode_amd.h
@@ -48,13 +48,12 @@ extern void __init load_ucode_amd_bsp(unsigned int family);
 extern void load_ucode_amd_ap(unsigned int family);
 extern int __init save_microcode_in_initrd_amd(unsigned int family);
 void reload_ucode_amd(unsigned int cpu);
-extern void amd_check_microcode(void);
 #else
 static inline void __init load_ucode_amd_bsp(unsigned int family) {}
 static inline void load_ucode_amd_ap(unsigned int family) {}
 static inline int __init
 save_microcode_in_initrd_amd(unsigned int family) { return -EINVAL; }
 static inline void reload_ucode_amd(unsigned int cpu) {}
-static inline void amd_check_microcode(void) {}
 #endif
+
 #endif /* _ASM_X86_MICROCODE_AMD_H */
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index d46300e94f853..36d52075fdade 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -682,9 +682,11 @@ extern u16 get_llc_id(unsigned int cpu);
 #ifdef CONFIG_CPU_SUP_AMD
 extern u32 amd_get_nodes_per_socket(void);
 extern u32 amd_get_highest_perf(void);
+extern void amd_check_microcode(void);
 #else
 static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
 static inline u32 amd_get_highest_perf(void)		{ return 0; }
+static inline void amd_check_microcode(void)		{ }
 #endif
 
 extern unsigned long arch_align_stack(unsigned long sp);
-- 
2.39.2