[PATCH] lib/crypto: x86/poly1305: Drop redundant checks for AVX and AVX2

[PATCH] lib/crypto: x86/poly1305: Drop redundant checks for AVX and AVX2

[Eric Biggers]

Reorganize the code in poly1305_mod_init_arch() to use nesting.  This
eliminates redundant boot_cpu_has() calls.  It also makes the code
structure more closely match poly1305_blocks(), which has an early
return if poly1305_use_avx isn't set.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
---
 lib/crypto/x86/poly1305.h | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/crypto/x86/poly1305.h b/lib/crypto/x86/poly1305.h
index 3b92e20f4f9b3..89d3b6add442a 100644
--- a/lib/crypto/x86/poly1305.h
+++ b/lib/crypto/x86/poly1305.h
@@ -143,13 +143,17 @@ static void poly1305_emit(const struct poly1305_state *ctx,
 #define poly1305_mod_init_arch poly1305_mod_init_arch
 static void poly1305_mod_init_arch(void)
 {
-	if (boot_cpu_has(X86_FEATURE_AVX))
+	if (boot_cpu_has(X86_FEATURE_AVX)) {
 		static_branch_enable(&poly1305_use_avx);
-	if (boot_cpu_has(X86_FEATURE_AVX) && boot_cpu_has(X86_FEATURE_AVX2))
-		static_branch_enable(&poly1305_use_avx2);
-	if (boot_cpu_has(X86_FEATURE_AVX) && boot_cpu_has(X86_FEATURE_AVX2) &&
-	    boot_cpu_has(X86_FEATURE_AVX512F) &&
-	    /* Skylake downclocks unacceptably much when using zmm, but later generations are fast. */
-	    boot_cpu_data.x86_vfm != INTEL_SKYLAKE_X)
-		static_branch_enable(&poly1305_use_avx512);
+		if (boot_cpu_has(X86_FEATURE_AVX2)) {
+			static_branch_enable(&poly1305_use_avx2);
+			/*
+			 * Skylake downclocks unacceptably much when using zmm,
+			 * but later generations are fast.
+			 */
+			if (boot_cpu_has(X86_FEATURE_AVX512F) &&
+			    boot_cpu_data.x86_vfm != INTEL_SKYLAKE_X)
+				static_branch_enable(&poly1305_use_avx512);
+		}
+	}
 }

base-commit: 33b4f31b1aea3f62b61c892daefc0e6a77859032
-- 
2.56.1

Re: [PATCH] lib/crypto: x86/poly1305: Drop redundant checks for AVX and AVX2

[Ard Biesheuvel]

On Wed, 11 Nov 2026, at 21:15, Eric Biggers wrote:
> Reorganize the code in poly1305_mod_init_arch() to use nesting.  This
> eliminates redundant boot_cpu_has() calls.  It also makes the code
> structure more closely match poly1305_blocks(), which has an early
> return if poly1305_use_avx isn't set.
>
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> ---
>  lib/crypto/x86/poly1305.h | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
>

Acked-by: Ard Biesheuvel <ardb@kernel.org>

Re: [PATCH] lib/crypto: x86/poly1305: Drop redundant checks for AVX and AVX2

[Eric Biggers]

On Wed, Nov 11, 2026 at 12:15:25PM -0800, Eric Biggers wrote:
> Reorganize the code in poly1305_mod_init_arch() to use nesting.  This
> eliminates redundant boot_cpu_has() calls.  It also makes the code
> structure more closely match poly1305_blocks(), which has an early
> return if poly1305_use_avx isn't set.
> 
> Signed-off-by: Eric Biggers <ebiggers@kernel.org>
> ---
>  lib/crypto/x86/poly1305.h | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next

- Eric