PS: You wrote that with the downgraded kernel it works again. I don't know in which way CONFIG_CRYPTO_SALSA20=m and CONFIG_CRYPTO_SALSA20_X86_64=m are related to each other, perhaps it's correct that CONFIG_CRYPTO_SALSA20_X86_64 isn't shown by the config of the build kernel. What's the output of uname -rm; zgrep SALSA /proc/config.gz for the downgraded kernel, that works for you?
