This is a note to let you know that I've just added the patch titled s390/archrandom: simplify back to earlier design and initialize earlier to the 4.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: s390-archrandom-simplify-back-to-earlier-design-and-initialize-earlier.patch and it can be found in the queue-4.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From e4f74400308cb8abde5fdc9cad609c2aba32110c Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" <Jason@xxxxxxxxx> Date: Sat, 11 Jun 2022 00:20:23 +0200 Subject: s390/archrandom: simplify back to earlier design and initialize earlier From: Jason A. Donenfeld <Jason@xxxxxxxxx> commit e4f74400308cb8abde5fdc9cad609c2aba32110c upstream. s390x appears to present two RNG interfaces: - a "TRNG" that gathers entropy using some hardware function; and - a "DRBG" that takes in a seed and expands it. Previously, the TRNG was wired up to arch_get_random_{long,int}(), but it was observed that this was being called really frequently, resulting in high overhead. So it was changed to be wired up to arch_get_random_ seed_{long,int}(), which was a reasonable decision. Later on, the DRBG was then wired up to arch_get_random_{long,int}(), with a complicated buffer filling thread, to control overhead and rate. Fortunately, none of the performance issues matter much now. The RNG always attempts to use arch_get_random_seed_{long,int}() first, which means a complicated implementation of arch_get_random_{long,int}() isn't really valuable or useful to have around. And it's only used when reseeding, which means it won't hit the high throughput complications that were faced before. So this commit returns to an earlier design of just calling the TRNG in arch_get_random_seed_{long,int}(), and returning false in arch_get_ random_{long,int}(). Part of what makes the simplification possible is that the RNG now seeds itself using the TRNG at bootup. But this only works if the TRNG is detected early in boot, before random_init() is called. So this commit also causes that check to happen in setup_arch(). Cc: stable@xxxxxxxxxxxxxxx Cc: Harald Freudenberger <freude@xxxxxxxxxxxxx> Cc: Ingo Franzki <ifranzki@xxxxxxxxxxxxx> Cc: Juergen Christ <jchrist@xxxxxxxxxxxxx> Cc: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Link: https://lore.kernel.org/r/20220610222023.378448-1-Jason@xxxxxxxxx Reviewed-by: Harald Freudenberger <freude@xxxxxxxxxxxxx> Acked-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx> Signed-off-by: Jason A. Donenfeld <Jason@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/s390/crypto/arch_random.c | 20 +++----------------- arch/s390/include/asm/archrandom.h | 32 ++++++++++++++------------------ arch/s390/kernel/setup.c | 5 +++++ 3 files changed, 22 insertions(+), 35 deletions(-) --- a/arch/s390/crypto/arch_random.c +++ b/arch/s390/crypto/arch_random.c @@ -1,13 +1,9 @@ +// SPDX-License-Identifier: GPL-2.0 /* * s390 arch random implementation. * - * Copyright IBM Corp. 2017 - * Author(s): Harald Freudenberger <freude@xxxxxxxxxx> - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License (version 2 only) - * as published by the Free Software Foundation. - * + * Copyright IBM Corp. 2017, 2020 + * Author(s): Harald Freudenberger */ #include <linux/kernel.h> @@ -20,13 +16,3 @@ DEFINE_STATIC_KEY_FALSE(s390_arch_random atomic64_t s390_arch_random_counter = ATOMIC64_INIT(0); EXPORT_SYMBOL(s390_arch_random_counter); - -static int __init s390_arch_random_init(void) -{ - /* check if subfunction CPACF_PRNO_TRNG is available */ - if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) - static_branch_enable(&s390_arch_random_available); - - return 0; -} -arch_initcall(s390_arch_random_init); --- a/arch/s390/include/asm/archrandom.h +++ b/arch/s390/include/asm/archrandom.h @@ -2,7 +2,7 @@ /* * Kernel interface for the s390 arch_random_* functions * - * Copyright IBM Corp. 2017 + * Copyright IBM Corp. 2017, 2020 * * Author: Harald Freudenberger <freude@xxxxxxxxxx> * @@ -20,38 +20,34 @@ DECLARE_STATIC_KEY_FALSE(s390_arch_random_available); extern atomic64_t s390_arch_random_counter; -static void s390_arch_random_generate(u8 *buf, unsigned int nbytes) +static inline bool __must_check arch_get_random_long(unsigned long *v) { - cpacf_trng(NULL, 0, buf, nbytes); - atomic64_add(nbytes, &s390_arch_random_counter); + return false; } -static inline bool arch_get_random_long(unsigned long *v) +static inline bool __must_check arch_get_random_int(unsigned int *v) { - if (static_branch_likely(&s390_arch_random_available)) { - s390_arch_random_generate((u8 *)v, sizeof(*v)); - return true; - } return false; } -static inline bool arch_get_random_int(unsigned int *v) +static inline bool __must_check arch_get_random_seed_long(unsigned long *v) { if (static_branch_likely(&s390_arch_random_available)) { - s390_arch_random_generate((u8 *)v, sizeof(*v)); + cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); + atomic64_add(sizeof(*v), &s390_arch_random_counter); return true; } return false; } -static inline bool arch_get_random_seed_long(unsigned long *v) +static inline bool __must_check arch_get_random_seed_int(unsigned int *v) { - return arch_get_random_long(v); -} - -static inline bool arch_get_random_seed_int(unsigned int *v) -{ - return arch_get_random_int(v); + if (static_branch_likely(&s390_arch_random_available)) { + cpacf_trng(NULL, 0, (u8 *)v, sizeof(*v)); + atomic64_add(sizeof(*v), &s390_arch_random_counter); + return true; + } + return false; } #endif /* CONFIG_ARCH_RANDOM */ --- a/arch/s390/kernel/setup.c +++ b/arch/s390/kernel/setup.c @@ -853,6 +853,11 @@ static void __init setup_randomness(void if (stsi(vmms, 3, 2, 2) == 0 && vmms->count) add_device_randomness(&vmms->vm, sizeof(vmms->vm[0]) * vmms->count); memblock_free((unsigned long) vmms, PAGE_SIZE); + +#ifdef CONFIG_ARCH_RANDOM + if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG)) + static_branch_enable(&s390_arch_random_available); +#endif } /* Patches currently in stable-queue which might be from Jason@xxxxxxxxx are queue-4.14/s390-archrandom-simplify-back-to-earlier-design-and-initialize-earlier.patch