Re: [PATCH 4/4] crypto: add support for nettle's native XTS impl

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 10/17/19 4:56 PM, Daniel P. Berrangé wrote:
> Nettle 3.5.0 will add support for the XTS mode. Use this because long
> term we wish to delete QEMU's XTS impl to avoid carrying private crypto
> algorithm impls.
> 
> Unfortunately this degrades nettle performance from 612 MB/s to 568 MB/s
> as nettle's XTS impl isn't so well optimized yet.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>   configure              | 18 ++++++++++++++++++
>   crypto/cipher-nettle.c | 18 ++++++++++++++++++
>   2 files changed, 36 insertions(+)
> 
> diff --git a/configure b/configure
> index 98edb0ff44..6650c72348 100755
> --- a/configure
> +++ b/configure
> @@ -471,6 +471,7 @@ gtk_gl="no"
>   tls_priority="NORMAL"
>   gnutls=""
>   nettle=""
> +nettle_xts="no"
>   gcrypt=""
>   gcrypt_hmac="no"
>   gcrypt_xts="no"
> @@ -2862,6 +2863,19 @@ if test "$nettle" != "no"; then
>               pass="yes"
>           fi
>       fi
> +    if test "$pass" = "yes"
> +    then
> +        cat > $TMPC << EOF
> +#include <nettle/xts.h>
> +int main(void) {
> +  return 0;
> +}
> +EOF
> +        if compile_prog "$nettle_cflags" "$nettle_libs" ; then
> +            nettle_xts=yes
> +            qemu_private_xts=no

Ah, now this variable makes sense.

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

> +        fi
> +    fi
>       if test "$pass" = "no" && test "$nettle" = "yes"; then
>           feature_not_found "nettle" "Install nettle devel >= 2.7.1"
>       else
> @@ -6337,6 +6351,10 @@ then
>      echo "  XTS             $gcrypt_xts"
>   fi
>   echo "nettle            $nettle $(echo_version $nettle $nettle_version)"
> +if test "$nettle" = "yes"
> +then
> +   echo "  XTS             $nettle_xts"
> +fi
>   echo "libtasn1          $tasn1"
>   echo "PAM               $auth_pam"
>   echo "iconv support     $iconv"
> diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c
> index d7411bb8ff..08794a9b10 100644
> --- a/crypto/cipher-nettle.c
> +++ b/crypto/cipher-nettle.c
> @@ -19,7 +19,9 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>   #include "crypto/xts.h"
> +#endif
>   #include "cipherpriv.h"
>   
>   #include <nettle/nettle-types.h>
> @@ -30,6 +32,9 @@
>   #include <nettle/serpent.h>
>   #include <nettle/twofish.h>
>   #include <nettle/ctr.h>
> +#ifndef CONFIG_QEMU_PRIVATE_XTS
> +#include <nettle/xts.h>
> +#endif
>   
>   typedef void (*QCryptoCipherNettleFuncWrapper)(const void *ctx,
>                                                  size_t length,
> @@ -626,9 +631,15 @@ qcrypto_nettle_cipher_encrypt(QCryptoCipher *cipher,
>           break;
>   
>       case QCRYPTO_CIPHER_MODE_XTS:
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>           xts_encrypt(ctx->ctx, ctx->ctx_tweak,
>                       ctx->alg_encrypt_wrapper, ctx->alg_encrypt_wrapper,
>                       ctx->iv, len, out, in);
> +#else
> +        xts_encrypt_message(ctx->ctx, ctx->ctx_tweak,
> +                            ctx->alg_encrypt_native,
> +                            ctx->iv, len, out, in);
> +#endif
>           break;
>   
>       case QCRYPTO_CIPHER_MODE_CTR:
> @@ -673,9 +684,16 @@ qcrypto_nettle_cipher_decrypt(QCryptoCipher *cipher,
>           break;
>   
>       case QCRYPTO_CIPHER_MODE_XTS:
> +#ifdef CONFIG_QEMU_PRIVATE_XTS
>           xts_decrypt(ctx->ctx, ctx->ctx_tweak,
>                       ctx->alg_encrypt_wrapper, ctx->alg_decrypt_wrapper,
>                       ctx->iv, len, out, in);
> +#else
> +        xts_decrypt_message(ctx->ctx, ctx->ctx_tweak,
> +                            ctx->alg_encrypt_native,
> +                            ctx->alg_decrypt_native,
> +                            ctx->iv, len, out, in);
> +#endif
>           break;
>       case QCRYPTO_CIPHER_MODE_CTR:
>           ctr_crypt(ctx->ctx, ctx->alg_encrypt_native,
>