linux-kernel - [PATCH] [v2] x86: coco: replace static const cc

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Message-Id: <20250310131114.2635497-1-arnd@kernel.org>
Date: Mon, 10 Mar 2025 14:10:59 +0100
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,
	Tom Lendacky <thomas.lendacky@....com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Elena Reshetova <elena.reshetova@...el.com>,
	"Jason A. Donenfeld" <Jason@...c4.com>,
	Yue Haibing <yuehaibing@...wei.com>,
	Juergen Gross <jgross@...e.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] [v2] x86: coco: replace static const cc_mask with a function

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

When extra warnings are enabled, the cc_mask definition in asm/coco.h
causes a build failure with gcc:

arch/x86/include/asm/coco.h:28:18: error: 'cc_mask' defined but not used [-Werror=unused-const-variable=]
   28 | static const u64 cc_mask = 0;

Add a cc_get_mask() function mirroring cc_set_mask() for the one
user of the variable outside of the coco implementation.

Fixes: a0a8d15a798b ("x86/tdx: Preserve shared bit on mprotect()")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
--
v2: use an inline helper instead of a __maybe_unused annotaiton.
---
 arch/x86/include/asm/coco.h          | 10 +++++++++-
 arch/x86/include/asm/pgtable_types.h |  2 +-
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/coco.h b/arch/x86/include/asm/coco.h
index aa6c8f8ca958..e7225452963f 100644
--- a/arch/x86/include/asm/coco.h
+++ b/arch/x86/include/asm/coco.h
@@ -15,6 +15,11 @@ enum cc_vendor {
 extern enum cc_vendor cc_vendor;
 extern u64 cc_mask;
 
+static inline u64 cc_get_mask(void)
+{
+	return cc_mask;
+}
+
 static inline void cc_set_mask(u64 mask)
 {
 	RIP_REL_REF(cc_mask) = mask;
@@ -25,7 +30,10 @@ u64 cc_mkdec(u64 val);
 void cc_random_init(void);
 #else
 #define cc_vendor (CC_VENDOR_NONE)
-static const u64 cc_mask = 0;
+static inline u64 cc_get_mask(void)
+{
+	return 0;
+}
 
 static inline u64 cc_mkenc(u64 val)
 {
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index c90e9c51edb7..74d461cc8e20 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -179,7 +179,7 @@ enum page_cache_mode {
 };
 #endif
 
-#define _PAGE_CC		(_AT(pteval_t, cc_mask))
+#define _PAGE_CC		(_AT(pteval_t, cc_get_mask()))
 #define _PAGE_ENC		(_AT(pteval_t, sme_me_mask))
 
 #define _PAGE_CACHE_MASK	(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)
-- 
2.39.5