diff mbox series

crypto: x86/chacha - Remove SIMD fallback path

Message ID Z-4LOoynbEz3ZLuQ@gondor.apana.org.au
State New
Headers show
Series crypto: x86/chacha - Remove SIMD fallback path | expand

Commit Message

Herbert Xu April 3, 2025, 4:14 a.m. UTC 
On Wed, Apr 02, 2025 at 08:59:34PM -0700, Eric Biggers wrote:
>
> But in a lot of cases there is also no reason to even add that restriction.  I'm
> not sure why you're so eager to make the library functions harder to use.

I have no intention of making any changes to siphash.  It doesn't
even use SIMD.

All I want to do is get rid of the crypto_simd_usable() fallback
paths that we currently have in arch/x86/crypto.  This code is
never used in hardirq context (and should never be).

For example:

---8<---
Get rid of the fallback path as SIMD is now always usable in softirq
context.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Comments

Eric Biggers April 7, 2025, 4:48 p.m. UTC | #1 
On Thu, Apr 03, 2025 at 12:14:50PM +0800, Herbert Xu wrote:
> On Wed, Apr 02, 2025 at 08:59:34PM -0700, Eric Biggers wrote:
> >
> > But in a lot of cases there is also no reason to even add that restriction.  I'm
> > not sure why you're so eager to make the library functions harder to use.
> 
> I have no intention of making any changes to siphash.  It doesn't
> even use SIMD.
> 
> All I want to do is get rid of the crypto_simd_usable() fallback
> paths that we currently have in arch/x86/crypto.  This code is
> never used in hardirq context (and should never be).
> 
> For example:
> 
> ---8<---
> Get rid of the fallback path as SIMD is now always usable in softirq
> context.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 

It looks like this broken patch already got applied for some reason.

First, there doesn't seem to be agreement yet that the library functions should
have requirements on the calling context.

Second, your patch made unrelated changes that deleted the checks for SSSE3
support.  Thus dropping support for CPUs that don't support SSSE3.

- Eric
diff mbox series

Patch

diff --git a/arch/x86/crypto/chacha_glue.c b/arch/x86/crypto/chacha_glue.c
index 8bb74a272879..6a3d60cf3192 100644
--- a/arch/x86/crypto/chacha_glue.c
+++ b/arch/x86/crypto/chacha_glue.c
@@ -6,9 +6,7 @@ 
  * Copyright (C) 2015 Martin Willi
  */
 
-#include <crypto/algapi.h>
 #include <crypto/internal/chacha.h>
-#include <crypto/internal/simd.h>
 #include <crypto/internal/skcipher.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -35,7 +33,6 @@  asmlinkage void chacha_4block_xor_avx512vl(u32 *state, u8 *dst, const u8 *src,
 asmlinkage void chacha_8block_xor_avx512vl(u32 *state, u8 *dst, const u8 *src,
 					   unsigned int len, int nrounds);
 
-static __ro_after_init DEFINE_STATIC_KEY_FALSE(chacha_use_simd);
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(chacha_use_avx2);
 static __ro_after_init DEFINE_STATIC_KEY_FALSE(chacha_use_avx512vl);
 
@@ -123,23 +120,15 @@  static void chacha_dosimd(u32 *state, u8 *dst, const u8 *src,
 
 void hchacha_block_arch(const u32 *state, u32 *stream, int nrounds)
 {
-	if (!static_branch_likely(&chacha_use_simd) || !crypto_simd_usable()) {
-		hchacha_block_generic(state, stream, nrounds);
-	} else {
-		kernel_fpu_begin();
-		hchacha_block_ssse3(state, stream, nrounds);
-		kernel_fpu_end();
-	}
+	kernel_fpu_begin();
+	hchacha_block_ssse3(state, stream, nrounds);
+	kernel_fpu_end();
 }
 EXPORT_SYMBOL(hchacha_block_arch);
 
 void chacha_crypt_arch(u32 *state, u8 *dst, const u8 *src, unsigned int bytes,
 		       int nrounds)
 {
-	if (!static_branch_likely(&chacha_use_simd) || !crypto_simd_usable() ||
-	    bytes <= CHACHA_BLOCK_SIZE)
-		return chacha_crypt_generic(state, dst, src, bytes, nrounds);
-
 	do {
 		unsigned int todo = min_t(unsigned int, bytes, SZ_4K);
 
@@ -171,18 +160,11 @@  static int chacha_simd_stream_xor(struct skcipher_request *req,
 		if (nbytes < walk.total)
 			nbytes = round_down(nbytes, walk.stride);
 
-		if (!static_branch_likely(&chacha_use_simd) ||
-		    !crypto_simd_usable()) {
-			chacha_crypt_generic(state, walk.dst.virt.addr,
-					     walk.src.virt.addr, nbytes,
-					     ctx->nrounds);
-		} else {
-			kernel_fpu_begin();
-			chacha_dosimd(state, walk.dst.virt.addr,
-				      walk.src.virt.addr, nbytes,
-				      ctx->nrounds);
-			kernel_fpu_end();
-		}
+		kernel_fpu_begin();
+		chacha_dosimd(state, walk.dst.virt.addr,
+			      walk.src.virt.addr, nbytes,
+			      ctx->nrounds);
+		kernel_fpu_end();
 		err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 	}
 
@@ -207,13 +189,9 @@  static int xchacha_simd(struct skcipher_request *req)
 
 	chacha_init(state, ctx->key, req->iv);
 
-	if (req->cryptlen > CHACHA_BLOCK_SIZE && crypto_simd_usable()) {
-		kernel_fpu_begin();
-		hchacha_block_ssse3(state, subctx.key, ctx->nrounds);
-		kernel_fpu_end();
-	} else {
-		hchacha_block_generic(state, subctx.key, ctx->nrounds);
-	}
+	kernel_fpu_begin();
+	hchacha_block_ssse3(state, subctx.key, ctx->nrounds);
+	kernel_fpu_end();
 	subctx.nrounds = ctx->nrounds;
 
 	memcpy(&real_iv[0], req->iv + 24, 8);
@@ -275,8 +253,6 @@  static int __init chacha_simd_mod_init(void)
 	if (!boot_cpu_has(X86_FEATURE_SSSE3))
 		return 0;
 
-	static_branch_enable(&chacha_use_simd);
-
 	if (boot_cpu_has(X86_FEATURE_AVX) &&
 	    boot_cpu_has(X86_FEATURE_AVX2) &&
 	    cpu_has_xfeatures(XFEATURE_MASK_SSE | XFEATURE_MASK_YMM, NULL)) {