From b095b2fe2ffba9738ba2c0dd5cc5f06e029c290b Mon Sep 17 00:00:00 2001
From: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Date: Tue, 20 Dec 2011 12:20:16 +0200
Subject: [PATCH] --- yaml --- r: 292239 b: refs/heads/master c:
 a522ee85ba979e7897a75b1c97db1b0304b68b5c h: refs/heads/master i:   292237:
 e93daff1dfdd18415744bdff9c7c698707d71b33   292235:
 a19e489e2efbe60387aa5519dc664fb629e83177   292231:
 a4a6af98c0f6b19f7f0a596ae05e59f21894dc35   292223:
 8e3795929ea525b2c504cc8d75c1573a7511b16c v: v3

---
 [refs]                                    |  2 +-
 trunk/arch/x86/crypto/twofish_glue_3way.c | 47 +++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index fd007e2b0b47..85396e8d5654 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f1df57d02a0f83e764b4dc9187f58665d70f190e
+refs/heads/master: a522ee85ba979e7897a75b1c97db1b0304b68b5c
diff --git a/trunk/arch/x86/crypto/twofish_glue_3way.c b/trunk/arch/x86/crypto/twofish_glue_3way.c
index 7fee8c152f93..0afd134d8c9c 100644
--- a/trunk/arch/x86/crypto/twofish_glue_3way.c
+++ b/trunk/arch/x86/crypto/twofish_glue_3way.c
@@ -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;