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crypto: twofish-x86_64-3way - blacklist pentium4 and atom

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Performance of twofish-x86_64-3way on Intel Pentium 4 and Atom is lower than
of twofish-x86_64 module. So blacklist these CPUs.

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 12:20:16 +02:00 committed by Herbert Xu
parent f1df57d02a
commit a522ee85ba
1 changed files with 47 additions and 0 deletions
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47
arch/x86/crypto/twofish_glue_3way.c
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@ -25,6 +25,7 @@
*
*/
#include <asm/processor.h>
#include <linux/crypto.h>
#include <linux/init.h>
#include <linux/module.h>
@ -637,10 +638,56 @@ static struct crypto_alg blk_xts_alg = {
},
};
static bool is_blacklisted_cpu(void)
{
if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL)
return false;
if (boot_cpu_data.x86 == 0x06 &&
(boot_cpu_data.x86_model == 0x1c ||
boot_cpu_data.x86_model == 0x26 ||
boot_cpu_data.x86_model == 0x36)) {
/*
* On Atom, twofish-3way is slower than original assembler
* implementation. Twofish-3way trades off some performance in
* storing blocks in 64bit registers to allow three blocks to
* be processed parallel. Parallel operation then allows gaining
* more performance than was trade off, on out-of-order CPUs.
* However Atom does not benefit from this parallellism and
* should be blacklisted.
*/
return true;
}
if (boot_cpu_data.x86 == 0x0f) {
/*
* On Pentium 4, twofish-3way is slower than original assembler
* implementation because excessive uses of 64bit rotate and
* left-shifts (which are really slow on P4) needed to store and
* handle 128bit block in two 64bit registers.
*/
return true;
}
return false;
}
static int force;
module_param(force, int, 0);
MODULE_PARM_DESC(force, "Force module load, ignore CPU blacklist");
int __init init(void)
{
int err;
if (!force && is_blacklisted_cpu()) {
printk(KERN_INFO
"twofish-x86_64-3way: performance on this CPU "
"would be suboptimal: disabling "
"twofish-x86_64-3way.\n");
return -ENODEV;
}
err = crypto_register_alg(&blk_ecb_alg);
if (err)
goto ecb_err;