From: Ard Biesheuvel <ardb@kernel.org>

Move away from calling kernel_neon_begin() and kernel_neon_end()
directly, and instead, use the newly introduced scoped_ksimd() API. This
permits arm64 to modify the kernel mode NEON API without affecting code
that is shared between ARM and arm64.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 crypto/aegis128-neon.c | 33 +++++++-------------
 1 file changed, 12 insertions(+), 21 deletions(-)

diff --git a/crypto/aegis128-neon.c b/crypto/aegis128-neon.c
index 9ee50549e823..b41807e63bd3 100644
--- a/crypto/aegis128-neon.c
+++ b/crypto/aegis128-neon.c
@@ -4,7 +4,7 @@
  */
 
 #include <asm/cpufeature.h>
-#include <asm/neon.h>
+#include <asm/simd.h>
 
 #include "aegis.h"
 #include "aegis-neon.h"
@@ -24,32 +24,28 @@ void crypto_aegis128_init_simd(struct aegis_state *state,
 			       const union aegis_block *key,
 			       const u8 *iv)
 {
-	kernel_neon_begin();
-	crypto_aegis128_init_neon(state, key, iv);
-	kernel_neon_end();
+	scoped_ksimd()
+		crypto_aegis128_init_neon(state, key, iv);
 }
 
 void crypto_aegis128_update_simd(struct aegis_state *state, const void *msg)
 {
-	kernel_neon_begin();
-	crypto_aegis128_update_neon(state, msg);
-	kernel_neon_end();
+	scoped_ksimd()
+		crypto_aegis128_update_neon(state, msg);
 }
 
 void crypto_aegis128_encrypt_chunk_simd(struct aegis_state *state, u8 *dst,
 					const u8 *src, unsigned int size)
 {
-	kernel_neon_begin();
-	crypto_aegis128_encrypt_chunk_neon(state, dst, src, size);
-	kernel_neon_end();
+	scoped_ksimd()
+		crypto_aegis128_encrypt_chunk_neon(state, dst, src, size);
 }
 
 void crypto_aegis128_decrypt_chunk_simd(struct aegis_state *state, u8 *dst,
 					const u8 *src, unsigned int size)
 {
-	kernel_neon_begin();
-	crypto_aegis128_decrypt_chunk_neon(state, dst, src, size);
-	kernel_neon_end();
+	scoped_ksimd()
+		crypto_aegis128_decrypt_chunk_neon(state, dst, src, size);
 }
 
 int crypto_aegis128_final_simd(struct aegis_state *state,
@@ -58,12 +54,7 @@ int crypto_aegis128_final_simd(struct aegis_state *state,
 			       unsigned int cryptlen,
 			       unsigned int authsize)
 {
-	int ret;
-
-	kernel_neon_begin();
-	ret = crypto_aegis128_final_neon(state, tag_xor, assoclen, cryptlen,
-					 authsize);
-	kernel_neon_end();
-
-	return ret;
+	scoped_ksimd()
+		return crypto_aegis128_final_neon(state, tag_xor, assoclen,
+						  cryptlen, authsize);
 }
-- 
2.51.0.618.g983fd99d29-goog

On Wed, Oct 01, 2025 at 11:02:06PM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> Move away from calling kernel_neon_begin() and kernel_neon_end()
> directly, and instead, use the newly introduced scoped_ksimd() API. This
> permits arm64 to modify the kernel mode NEON API without affecting code
> that is shared between ARM and arm64.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
>  crypto/aegis128-neon.c | 33 +++++++-------------
>  1 file changed, 12 insertions(+), 21 deletions(-)
> 
> diff --git a/crypto/aegis128-neon.c b/crypto/aegis128-neon.c
> index 9ee50549e823..b41807e63bd3 100644
> --- a/crypto/aegis128-neon.c
> +++ b/crypto/aegis128-neon.c
> @@ -4,7 +4,7 @@
>   */
>  
>  #include <asm/cpufeature.h>
> -#include <asm/neon.h>
> +#include <asm/simd.h>
>  
>  #include "aegis.h"
>  #include "aegis-neon.h"
> @@ -24,32 +24,28 @@ void crypto_aegis128_init_simd(struct aegis_state *state,
>  			       const union aegis_block *key,
>  			       const u8 *iv)
>  {
> -	kernel_neon_begin();
> -	crypto_aegis128_init_neon(state, key, iv);
> -	kernel_neon_end();
> +	scoped_ksimd()
> +		crypto_aegis128_init_neon(state, key, iv);
>  }

For these cases (to avoid the indentation change), do you want to use
just "guard" instead of "scope_guard", or do you want to explicitly
require explicit scope context even when the scope ends at the function
return?

-- 
Kees Cook

On Thu, 2 Oct 2025 at 18:20, Kees Cook <kees@kernel.org> wrote:
>
> On Wed, Oct 01, 2025 at 11:02:06PM +0200, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@kernel.org>
> >
> > Move away from calling kernel_neon_begin() and kernel_neon_end()
> > directly, and instead, use the newly introduced scoped_ksimd() API. This
> > permits arm64 to modify the kernel mode NEON API without affecting code
> > that is shared between ARM and arm64.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> >  crypto/aegis128-neon.c | 33 +++++++-------------
> >  1 file changed, 12 insertions(+), 21 deletions(-)
> >
> > diff --git a/crypto/aegis128-neon.c b/crypto/aegis128-neon.c
> > index 9ee50549e823..b41807e63bd3 100644
> > --- a/crypto/aegis128-neon.c
> > +++ b/crypto/aegis128-neon.c
> > @@ -4,7 +4,7 @@
> >   */
> >
> >  #include <asm/cpufeature.h>
> > -#include <asm/neon.h>
> > +#include <asm/simd.h>
> >
> >  #include "aegis.h"
> >  #include "aegis-neon.h"
> > @@ -24,32 +24,28 @@ void crypto_aegis128_init_simd(struct aegis_state *state,
> >                              const union aegis_block *key,
> >                              const u8 *iv)
> >  {
> > -     kernel_neon_begin();
> > -     crypto_aegis128_init_neon(state, key, iv);
> > -     kernel_neon_end();
> > +     scoped_ksimd()
> > +             crypto_aegis128_init_neon(state, key, iv);
> >  }
>
> For these cases (to avoid the indentation change), do you want to use
> just "guard" instead of "scope_guard", or do you want to explicitly
> require explicit scope context even when the scope ends at the function
> return?
>

I'm on the fence tbh. I think for future maintainability, being forced
to define the scope is perhaps better but in this case, the whole
function contains only a single line so there is little room for
confusion.