s390/crc32: Remove have_vxrs static key

Replace the have_vxrs static key with a cpu_has_vx() call.  cpu_has_vx()
resolves into a compile time constant (true) if the kernel is compiled
for z13 or newer.  Otherwise it generates an unconditional one
instruction branch, which is patched based on CPU alternatives.

In any case the generated code is at least as good as before and avoids
static key handling.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Link: https://lore.kernel.org/r/20250417125318.12521F12-hca@linux.ibm.com/
Signed-off-by: Eric Biggers <ebiggers@google.com>

diff --git a/arch/s390/lib/crc32-glue.c b/arch/s390/lib/crc32-glue.c
index 8f20a8e595c38c49f4cdb3e081b2c1c8b5eb889e..649ed7e8b99c878bff19690cbb289ee6eeee0609 100644 (file)
--- a/arch/s390/lib/crc32-glue.c
+++ b/arch/s390/lib/crc32-glue.c
@@ -18,8 +18,6 @@
 #define VX_ALIGNMENT           16L
 #define VX_ALIGN_MASK          (VX_ALIGNMENT - 1)
 
-static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_vxrs);
-
 /*
  * DEFINE_CRC32_VX() - Define a CRC-32 function using the vector extension
  *
@@ -34,8 +32,7 @@ static __ro_after_init DEFINE_STATIC_KEY_FALSE(have_vxrs);
                unsigned long prealign, aligned, remaining;                 \
                DECLARE_KERNEL_FPU_ONSTACK16(vxstate);                      \
                                                                            \
-               if (datalen < VX_MIN_LEN + VX_ALIGN_MASK ||                 \
-                   !static_branch_likely(&have_vxrs))                      \
+               if (datalen < VX_MIN_LEN + VX_ALIGN_MASK || !cpu_has_vx())  \
                        return ___crc32_sw(crc, data, datalen);             \
                                                                            \
                if ((unsigned long)data & VX_ALIGN_MASK) {                  \
@@ -66,8 +63,6 @@ DEFINE_CRC32_VX(crc32c_arch, crc32c_le_vgfm_16, crc32c_base)
 
 static int __init crc32_s390_init(void)
 {
-       if (cpu_have_feature(S390_CPU_FEATURE_VXRS))
-               static_branch_enable(&have_vxrs);
        return 0;
 }
 arch_initcall(crc32_s390_init);
@@ -79,10 +74,11 @@ module_exit(crc32_s390_exit);
 
 u32 crc32_optimizations(void)
 {
-       if (static_key_enabled(&have_vxrs))
+       if (cpu_has_vx()) {
                return CRC32_LE_OPTIMIZATION |
                       CRC32_BE_OPTIMIZATION |
                       CRC32C_OPTIMIZATION;
+       }
        return 0;
 }
 EXPORT_SYMBOL(crc32_optimizations);