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