crypto: blowfish-x86_64 - blacklist Pentium 4

Implementation in blowfish-x86_64 uses 64bit rotations which are slow on P4,
making blowfish-x86_64 slower than generic C implementation. Therefore
blacklist P4.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/arch/x86/crypto/blowfish_glue.c b/arch/x86/crypto/blowfish_glue.c
index b05aa163d55a304c224f4b79dfd40a408fc305c6..2970110d2cea465ac4cbf75803910455ab82177a 100644 (file)
--- a/arch/x86/crypto/blowfish_glue.c
+++ b/arch/x86/crypto/blowfish_glue.c
@@ -25,6 +25,7 @@
  *
  */
 
+#include <asm/processor.h>
 #include <crypto/blowfish.h>
 #include <linux/crypto.h>
 #include <linux/init.h>
@@ -446,10 +447,39 @@ static struct crypto_alg blk_ctr_alg = {
        },
 };
 
+static bool is_blacklisted_cpu(void)
+{
+       if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
+               return false;
+
+       if (boot_cpu_data.x86 == 0x0f) {
+               /*
+                * On Pentium 4, blowfish-x86_64 is slower than generic C
+                * implementation because use of 64bit rotates (which are really
+                * slow on P4). Therefore blacklist P4s.
+                */
+               return true;
+       }
+
+       return false;
+}
+
+static int force;
+module_param(force, int, 0);
+MODULE_PARM_DESC(force, "Force module load, ignore CPU blacklist");
+
 static int __init init(void)
 {
        int err;
 
+       if (!force && is_blacklisted_cpu()) {
+               printk(KERN_INFO
+                       "blowfish-x86_64: performance on this CPU "
+                       "would be suboptimal: disabling "
+                       "blowfish-x86_64.\n");
+               return -ENODEV;
+       }
+
        err = crypto_register_alg(&bf_alg);
        if (err)
                goto bf_err;