x86: coco: replace static const cc_mask with a function

[PATCH] [v2] x86: coco: replace static const cc_mask with a function

Posted by Arnd Bergmann 11 months ago

From: Arnd Bergmann <arnd@arndb.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@arndb.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

Re: [PATCH] [v2] x86: coco: replace static const cc_mask with a function

Posted by Sathyanarayanan Kuppuswamy 11 months ago

On 3/10/25 6:10 AM, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> --

Reviewed-by: Kuppuswamy Sathyanarayanan 
<sathyanarayanan.kuppuswamy@linux.intel.com>

> 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)

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer

Re: [PATCH] [v2] x86: coco: replace static const cc_mask with a function

Posted by Kirill A. Shutemov 11 months ago

On Mon, Mar 10, 2025 at 02:10:59PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.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@arndb.de>
> --
> v2: use an inline helper instead of a __maybe_unused annotaiton.

Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

[tip: x86/cleanups] x86/coco: Replace 'static const cc_mask' with the newly introduced cc_get_mask() function

Posted by tip-bot2 for Arnd Bergmann 11 months ago

The following commit has been merged into the x86/cleanups branch of tip:

Commit-ID:     ec73859d76db768da97ee799a91eb9c7d28974fe
Gitweb:        https://git.kernel.org/tip/ec73859d76db768da97ee799a91eb9c7d28974fe
Author:        Arnd Bergmann <arnd@arndb.de>
AuthorDate:    Mon, 10 Mar 2025 14:10:59 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 10 Mar 2025 20:06:47 +01:00

x86/coco: Replace 'static const cc_mask' with the newly introduced cc_get_mask() function

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@arndb.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20250310131114.2635497-1-arnd@kernel.org

--
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 aa6c8f8..e722545 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 4b80453..9c4d9fa 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -177,7 +177,7 @@ 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)