arm64/fpsimd: Avoid warning when sve_to_fpsimd() is unused

Historically fpsimd_to_sve() and sve_to_fpsimd() were (conditionally)
called by functions which were defined regardless of CONFIG_ARM64_SVE.
Hence it was necessary that both fpsimd_to_sve() and sve_to_fpsimd()
were always defined and not guarded by ifdeffery.

As a result of the removal of fpsimd_signal_preserve_current_state() in
commit:

  929fa99b1215966f ("arm64/fpsimd: signal: Always save+flush state early")

... sve_to_fpsimd() has no callers when CONFIG_ARM64_SVE=n, resulting in
a build-time warnign that it is unused:

| arch/arm64/kernel/fpsimd.c:676:13: warning: unused function 'sve_to_fpsimd' [-Wunused-function]
|   676 | static void sve_to_fpsimd(struct task_struct *task)
|       |             ^~~~~~~~~~~~~
| 1 warning generated.

In contrast, fpsimd_to_sve() still has callers which are defined when
CONFIG_ARM64_SVE=n, and it would be awkward to hide this behind
ifdeffery and/or to use stub functions.

For now, suppress the warning by marking both fpsimd_to_sve() and
sve_to_fpsimd() as 'static inline', as we usually do for stub functions.
The compiler will no longer warn if either function is unused.

Aside from suppressing the warning, there should be no functional change
as a result of this patch.

Link: https://lore.kernel.org/linux-arm-kernel/20250429194600.GA26883@willie-the-truck/
Reported-by: Will Deacon <will@kernel.org>
Fixes: 929fa99b1215 ("arm64/fpsimd: signal: Always save+flush state early")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20250430173240.4023627-1-mark.rutland@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index b0874402f7ecc7925d70e5674a30f46e37c6f9e6..422b9d43b1e644faab5c4e87fdbe4db99d49a695 100644 (file)
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -649,7 +649,7 @@ static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst,
  * task->thread.uw.fpsimd_state must be up to date before calling this
  * function.
  */
-static void fpsimd_to_sve(struct task_struct *task)
+static inline void fpsimd_to_sve(struct task_struct *task)
 {
        unsigned int vq;
        void *sst = task->thread.sve_state;
@@ -673,7 +673,7 @@ static void fpsimd_to_sve(struct task_struct *task)
  * bytes of allocated kernel memory.
  * task->thread.sve_state must be up to date before calling this function.
  */
-static void sve_to_fpsimd(struct task_struct *task)
+static inline void sve_to_fpsimd(struct task_struct *task)
 {
        unsigned int vq, vl;
        void const *sst = task->thread.sve_state;