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Commit a522ee85 authored by Jussi Kivilinna's avatar Jussi Kivilinna Committed by Herbert Xu
Browse files

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



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: default avatarJussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent f1df57d0

arch/x86/crypto/twofish_glue_3way.c

+47 −0
Original line number Diff line number Diff line
@@ -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;