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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id DA037C43334 for ; Tue, 19 Jul 2022 13:50:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=XYYfgyf7QM0ljKT73EdJoioF8RQJLdiGBQXbawVqwKU=; b=arAkp98k1QZ848 skDjNcmikKGh/h++FBMe4lH61GSt/B3kqL2XN9ZU/oW6V9ok+nGC9szxcGKpCgtLRkU/CqVVyHDO3 3KCgWtzfEuGN6JG3cSetxY3fIhKO4v8WOr9Zzp/R4xY28cgRFKP1CcexeP4BF1OtounMSX2L31l3b 6RCqrMvIVvPe5a2iBvJ/Qta7EimUTtuwQy9FgGlK4KZXri/4Nno5AESYrqn79aqe3pOnSm3+Is52c 5fyjZo+77Pj2tujHHeWRSsQySrcM25RacKrJsZy8v+rQBnrOYSly/hoYi1vlJ87KZEND6i5M2HYZ+ V+bkFpKyuDnv6OpWMl3g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1oDnar-009LHJ-PD; Tue, 19 Jul 2022 13:48:57 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1oDnao-009LFX-Ik for linux-arm-kernel@lists.infradead.org; Tue, 19 Jul 2022 13:48:56 +0000 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 ams.source.kernel.org (Postfix) with ESMTPS id DD5BBB819B8; 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-Disposition: inline In-Reply-To: <20220719130207.147536-1-Jason@zx2c4.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220719_064854_763424_68960D24 X-CRM114-Status: GOOD ( 19.29 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel