From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85F0DC43334 for ; Tue, 19 Jul 2022 14:17:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230049AbiGSORd (ORCPT ); Tue, 19 Jul 2022 10:17:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60328 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229895AbiGSORM (ORCPT ); Tue, 19 Jul 2022 10:17:12 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D0E0274CEC; Tue, 19 Jul 2022 06:48:50 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 530626165E; Tue, 19 Jul 2022 13:48:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 562EDC341CA; Tue, 19 Jul 2022 13:48:46 +0000 (UTC) Date: Tue, 19 Jul 2022 14:48:42 +0100 From: Catalin Marinas To: "Jason A. Donenfeld" Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, x86@kernel.org, Will Deacon , Alexander Gordeev , Thomas Gleixner , "H . Peter Anvin" , Borislav Petkov , Heiko Carstens , Johannes Berg , Mark Rutland , Harald Freudenberger , Michael Ellerman Subject: Re: [PATCH v3] random: handle archrandom with multiple longs Message-ID: References: <20220719130207.147536-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220719130207.147536-1-Jason@zx2c4.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 19, 2022 at 03:02:07PM +0200, Jason A. Donenfeld wrote: > The archrandom interface was originally designed for x86, which supplies > RDRAND/RDSEED for receiving random words into registers, resulting in > one function to generate an int and another to generate a long. However, > other architectures don't follow this. > > On arm64, the SMCCC TRNG interface can return between 1 and 3 longs. On > s390, the CPACF TRNG interface can return arbitrary amounts, with 32 > longs having the same cost as one. On UML, the os_getrandom() interface > can return arbitrary amounts. > > So change the api signature to take a "max_longs" parameter designating > the maximum number of longs requested, and then return the number of > longs generated. > > Since callers need to check this return value and loop anyway, each arch > implementation does not bother implementing its own loop to try again to > fill the maximum number of longs. Additionally, all existing callers > pass in a constant max_longs parameter. Taken together, these two things > mean that the codegen doesn't really change much for one-word-at-a-time > platforms, while performance is greatly improved on platforms such as > s390. > > Cc: Will Deacon > Cc: Alexander Gordeev > Cc: Thomas Gleixner > Cc: H. Peter Anvin > Cc: Catalin Marinas > Cc: Borislav Petkov > Cc: Heiko Carstens > Cc: Johannes Berg > Cc: Mark Rutland > Cc: Harald Freudenberger > Acked-by: Michael Ellerman > Signed-off-by: Jason A. Donenfeld For arm64: Acked-by: Catalin Marinas