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 37825C43334 for ; Mon, 18 Jul 2022 06:31:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233499AbiGRGbW (ORCPT ); Mon, 18 Jul 2022 02:31:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49412 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232841AbiGRGbV (ORCPT ); Mon, 18 Jul 2022 02:31:21 -0400 Received: from gandalf.ozlabs.org (gandalf.ozlabs.org [150.107.74.76]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 874CD2DCF; Sun, 17 Jul 2022 23:31:19 -0700 (PDT) Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 4LmXD32nd5z4xXF; Mon, 18 Jul 2022 16:31:15 +1000 (AEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ellerman.id.au; s=201909; t=1658125878; bh=k/N2K3A9Z5dV/oTr9hSFt64T6vlj0t235fSbwzPjkEA=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=rhhdlO5yl1t520u8BwcWmo9I5ryGffVzXJ8RE1EukbGFkVthHUiVLAjQDW9mzbv/g OWnQlMsP8NiwLcTMDx/u2JG1Y845X4k4XCnsJBoiWa8UdmP575Nw0RWGtzsUbxe3Jo bjBoqD+2lq0gKxXSMd0ODRCH8GSL8M6V7sL4NgfhjmUAkga44TSCl7UfnulRjDEHIo FCaFHm+TySK1rfoT4o+dES2ZEbTrcYCPeHtbeg4lIr9pHGtIWMcl595MciqG3LLg/f VdNtecuoOERxk91eMns13YSoniRlSGOaiEJZ8DZNFdGSbyIrboLkLaefUXVezPcmCK 4YiA9QdovohVg== From: Michael Ellerman To: "Jason A. Donenfeld" , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, x86@kernel.org Cc: "Jason A. Donenfeld" , Will Deacon , Alexander Gordeev , Thomas Gleixner , "H . Peter Anvin" , Catalin Marinas , Borislav Petkov , Heiko Carstens , Johannes Berg , Harald Freudenberger Subject: Re: [PATCH v2] random: handle archrandom in plural words In-Reply-To: <20220717200356.75060-1-Jason@zx2c4.com> References: <20220717200356.75060-1-Jason@zx2c4.com> Date: Mon, 18 Jul 2022 16:31:11 +1000 Message-ID: <87a697dj9s.fsf@mpe.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Jason A. Donenfeld" writes: > 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 words. On > s390, the CPACF TRNG interface can return between 1 and 32 words for the > same cost as for one word. On UML, the os_getrandom() interface can return > arbitrary amounts. > > So change the api signature to take a "words" parameter designating the > maximum number of words requested, and then return the number of words > generated. On powerpc a word is 32-bits and a doubleword is 64-bits (at least according to the ISA). I think that's also true on other 64-bit architectures. You could avoid any confusion by defining the API in terms of "longs" rather than "words". But that's just a comment, see what others think. > arch/powerpc/include/asm/archrandom.h | 30 ++------ > arch/powerpc/kvm/book3s_hv.c | 2 +- Acked-by: Michael Ellerman (powerpc) cheers