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crypto: blowfish-x86_64 - blacklist Pentium 4

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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>
This commit is contained in:
Jussi Kivilinna 2011-12-20 12:20:21 +02:00 committed by Herbert Xu
parent a522ee85ba
commit 4c58464b80
1 changed files with 30 additions and 0 deletions
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30
arch/x86/crypto/blowfish_glue.c
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@ -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;