Re: [PATCH RFC 13/15] powerpc: enable_kernel_altivec() requires disabled preemption

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2015-05-06 at 19:50 +0200, David Hildenbrand wrote:
> enable_kernel_altivec() has to be called with disabled preemption.
> Let's make this explicit, to prepare for pagefault_disable() not
> touching preemption anymore.
>
> Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>

Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

> ---
>  arch/powerpc/lib/vmx-helper.c | 11 ++++++-----
>  drivers/crypto/vmx/aes.c      |  8 +++++++-
>  drivers/crypto/vmx/aes_cbc.c  |  6 ++++++
>  drivers/crypto/vmx/ghash.c    |  8 ++++++++
>  4 files changed, 27 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/lib/vmx-helper.c b/arch/powerpc/lib/vmx-helper.c
> index 3cf529c..ac93a3b 100644
> --- a/arch/powerpc/lib/vmx-helper.c
> +++ b/arch/powerpc/lib/vmx-helper.c
> @@ -27,11 +27,11 @@ int enter_vmx_usercopy(void)
>  	if (in_interrupt())
>  		return 0;
>  
> -	/* This acts as preempt_disable() as well and will make
> -	 * enable_kernel_altivec(). We need to disable page faults
> -	 * as they can call schedule and thus make us lose the VMX
> -	 * context. So on page faults, we just fail which will cause
> -	 * a fallback to the normal non-vmx copy.
> +	preempt_disable();
> +	/*
> +	 * We need to disable page faults as they can call schedule and
> +	 * thus make us lose the VMX context. So on page faults, we just
> +	 * fail which will cause a fallback to the normal non-vmx copy.
>  	 */
>  	pagefault_disable();
>  
> @@ -47,6 +47,7 @@ int enter_vmx_usercopy(void)
>  int exit_vmx_usercopy(void)
>  {
>  	pagefault_enable();
> +	preempt_enable();
>  	return 0;
>  }
>  
> diff --git a/drivers/crypto/vmx/aes.c b/drivers/crypto/vmx/aes.c
> index ab300ea..a9064e3 100644
> --- a/drivers/crypto/vmx/aes.c
> +++ b/drivers/crypto/vmx/aes.c
> @@ -78,12 +78,14 @@ static int p8_aes_setkey(struct crypto_tfm *tfm, const u8 *key,
>      int ret;
>      struct p8_aes_ctx *ctx = crypto_tfm_ctx(tfm);
>  
> +    preempt_disable();
>      pagefault_disable();
>      enable_kernel_altivec();
>      ret = aes_p8_set_encrypt_key(key, keylen * 8, &ctx->enc_key);
>      ret += aes_p8_set_decrypt_key(key, keylen * 8, &ctx->dec_key);
>      pagefault_enable();
> -    
> +    preempt_enable();
> +
>      ret += crypto_cipher_setkey(ctx->fallback, key, keylen);
>      return ret;
>  }
> @@ -95,10 +97,12 @@ static void p8_aes_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
>      if (in_interrupt()) {
>          crypto_cipher_encrypt_one(ctx->fallback, dst, src);
>      } else {
> +	preempt_disable();
>          pagefault_disable();
>          enable_kernel_altivec();
>          aes_p8_encrypt(src, dst, &ctx->enc_key);
>          pagefault_enable();
> +	preempt_enable();
>      }
>  }
>  
> @@ -109,10 +113,12 @@ static void p8_aes_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
>      if (in_interrupt()) {
>          crypto_cipher_decrypt_one(ctx->fallback, dst, src);
>      } else {
> +	preempt_disable();
>          pagefault_disable();
>          enable_kernel_altivec();
>          aes_p8_decrypt(src, dst, &ctx->dec_key);
>          pagefault_enable();
> +	preempt_enable();
>      }
>  }
>  
> diff --git a/drivers/crypto/vmx/aes_cbc.c b/drivers/crypto/vmx/aes_cbc.c
> index 1a559b7..477284a 100644
> --- a/drivers/crypto/vmx/aes_cbc.c
> +++ b/drivers/crypto/vmx/aes_cbc.c
> @@ -79,11 +79,13 @@ static int p8_aes_cbc_setkey(struct crypto_tfm *tfm, const u8 *key,
>      int ret;
>      struct p8_aes_cbc_ctx *ctx = crypto_tfm_ctx(tfm);
>  
> +    preempt_disable();
>      pagefault_disable();
>      enable_kernel_altivec();
>      ret = aes_p8_set_encrypt_key(key, keylen * 8, &ctx->enc_key);
>      ret += aes_p8_set_decrypt_key(key, keylen * 8, &ctx->dec_key);
>      pagefault_enable();
> +    preempt_enable();
>  
>      ret += crypto_blkcipher_setkey(ctx->fallback, key, keylen);
>      return ret;
> @@ -106,6 +108,7 @@ static int p8_aes_cbc_encrypt(struct blkcipher_desc *desc,
>      if (in_interrupt()) {
>          ret = crypto_blkcipher_encrypt(&fallback_desc, dst, src, nbytes);
>      } else {
> +	preempt_disable();
>          pagefault_disable();
>          enable_kernel_altivec();
>  
> @@ -119,6 +122,7 @@ static int p8_aes_cbc_encrypt(struct blkcipher_desc *desc,
>  	}
>  
>          pagefault_enable();
> +	preempt_enable();
>      }
>  
>      return ret;
> @@ -141,6 +145,7 @@ static int p8_aes_cbc_decrypt(struct blkcipher_desc *desc,
>      if (in_interrupt()) {
>          ret = crypto_blkcipher_decrypt(&fallback_desc, dst, src, nbytes);
>      } else {
> +	preempt_disable();
>          pagefault_disable();
>          enable_kernel_altivec();
>  
> @@ -154,6 +159,7 @@ static int p8_aes_cbc_decrypt(struct blkcipher_desc *desc,
>  		}
>  
>          pagefault_enable();
> +	preempt_enable();
>      }
>  
>      return ret;
> diff --git a/drivers/crypto/vmx/ghash.c b/drivers/crypto/vmx/ghash.c
> index d0ffe27..f255ec4 100644
> --- a/drivers/crypto/vmx/ghash.c
> +++ b/drivers/crypto/vmx/ghash.c
> @@ -114,11 +114,13 @@ static int p8_ghash_setkey(struct crypto_shash *tfm, const u8 *key,
>      if (keylen != GHASH_KEY_LEN)
>          return -EINVAL;
>  
> +    preempt_disable();
>      pagefault_disable();
>      enable_kernel_altivec();
>      enable_kernel_fp();
>      gcm_init_p8(ctx->htable, (const u64 *) key);
>      pagefault_enable();
> +    preempt_enable();
>      return crypto_shash_setkey(ctx->fallback, key, keylen);
>  }
>  
> @@ -140,23 +142,27 @@ static int p8_ghash_update(struct shash_desc *desc,
>              }
>              memcpy(dctx->buffer + dctx->bytes, src,
>                      GHASH_DIGEST_SIZE - dctx->bytes);
> +	    preempt_disable();
>              pagefault_disable();
>              enable_kernel_altivec();
>              enable_kernel_fp();
>              gcm_ghash_p8(dctx->shash, ctx->htable, dctx->buffer,
>                      GHASH_DIGEST_SIZE);
>              pagefault_enable();
> +	    preempt_enable();
>              src += GHASH_DIGEST_SIZE - dctx->bytes;
>              srclen -= GHASH_DIGEST_SIZE - dctx->bytes;
>              dctx->bytes = 0;
>          }
>          len = srclen & ~(GHASH_DIGEST_SIZE - 1);
>          if (len) {
> +	    preempt_disable();
>              pagefault_disable();
>              enable_kernel_altivec();
>              enable_kernel_fp();
>              gcm_ghash_p8(dctx->shash, ctx->htable, src, len);
>              pagefault_enable();
> +	    preempt_enable();
>              src += len;
>              srclen -= len;
>          }
> @@ -180,12 +186,14 @@ static int p8_ghash_final(struct shash_desc *desc, u8 *out)
>          if (dctx->bytes) {
>              for (i = dctx->bytes; i < GHASH_DIGEST_SIZE; i++)
>                  dctx->buffer[i] = 0;
> +	    preempt_disable();
>              pagefault_disable();
>              enable_kernel_altivec();
>              enable_kernel_fp();
>              gcm_ghash_p8(dctx->shash, ctx->htable, dctx->buffer,
>                      GHASH_DIGEST_SIZE);
>              pagefault_enable();
> +	    preempt_enable();
>              dctx->bytes = 0;
>          }
>          memcpy(out, dctx->shash, GHASH_DIGEST_SIZE);


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