sched/preempt, powerpc: Disable preemption in enable_kernel_altivec() explicitly

enable_kernel_altivec() has to be called with disabled preemption.
Let's make this explicit, to prepare for pagefault_disable() not
touching preemption anymore.

Reviewed-and-tested-by: Thomas Gleixner <[e-mail]>
Signed-off-by: David Hildenbrand <[e-mail]>
Signed-off-by: Peter Zijlstra (Intel) <[e-mail]>
Acked-by: Benjamin Herrenschmidt <[e-mail]>
Cc: [e-mail]
Cc: Linus Torvalds <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Cc: [e-mail]
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

arch/powerpc/lib/vmx-helper.c

···
 	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();
 
···
 int exit_vmx_usercopy(void)
 {
 	pagefault_enable();
+	preempt_enable();
 	return 0;
 }
 

drivers/crypto/vmx/aes.c

···
     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;
 }
···
     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();
     }
 }
 
···
     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();
     }
 }
 

drivers/crypto/vmx/aes_cbc.c

···
     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;
···
     if (in_interrupt()) {
         ret = crypto_blkcipher_encrypt(&fallback_desc, dst, src, nbytes);
     } else {
+	preempt_disable();
         pagefault_disable();
         enable_kernel_altivec();
 
···
 	}
 
         pagefault_enable();
+	preempt_enable();
     }
 
     return ret;
···
     if (in_interrupt()) {
         ret = crypto_blkcipher_decrypt(&fallback_desc, dst, src, nbytes);
     } else {
+	preempt_disable();
         pagefault_disable();
         enable_kernel_altivec();
 
···
 		}
 
         pagefault_enable();
+	preempt_enable();
     }
 
     return ret;

drivers/crypto/vmx/ghash.c

···
     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);
 }
 
···
             }
             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;
         }
···
         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);