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 3EE67C4332F for ; Tue, 19 Apr 2022 11:34:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344814AbiDSLgz (ORCPT ); Tue, 19 Apr 2022 07:36:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235055AbiDSLgy (ORCPT ); Tue, 19 Apr 2022 07:36:54 -0400 Received: from sipsolutions.net (s3.sipsolutions.net [IPv6:2a01:4f8:191:4433::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2FCD02E9C9; Tue, 19 Apr 2022 04:34:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sipsolutions.net; s=mail; h=Content-Transfer-Encoding:MIME-Version: Content-Type:References:In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-To: Resent-Cc:Resent-Message-ID; bh=PBEaZlFaHYvw3+tY3UhjQeVca+KaL0Du1BTdeZIcC7U=; t=1650368051; x=1651577651; b=sfd1r0tjdRraJErLzIANMDeOfosZEMb0ui5naTY2Sv8s1iq ZQioNRVtMzu7mArCV2oZOA5f4Kc4lvB62uJmdDSVceTw1XyW8DJnGSgv2dT+tzHR+6nly5Fb+RQH0 /K1/CWN5jCuIGac6qOaw8rWSnslEkeS9CMwbSgLfzdgmjgSZwwBsdmeFEIHW3it8vLR5yNchX36PJ RaqoFLdtI6GL9kKDGCa/IyvPG6z5wQ2yOZH3Tg3gg6b7NS0QzW5f6PCqdziEWNHBS0pzC9ce65O0U KkE6kQYQ9mnhWQaLoVgiPWDi1rbO4NT9B4YGlILW31ICGdTVvqwpVKP+ak4aLhwg==; Received: by sipsolutions.net with esmtpsa (TLS1.3:ECDHE_SECP256R1__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.95) (envelope-from ) id 1ngm6l-00BueY-OI; Tue, 19 Apr 2022 13:33:23 +0200 Message-ID: <694c2318d98973ee8995e891f81216ad267341dc.camel@sipsolutions.net> Subject: Re: [PATCH v5 08/11] um: use fallback for random_get_entropy() instead of zero From: Johannes Berg To: "Jason A. Donenfeld" , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, tglx@linutronix.de, arnd@arndb.de Cc: Theodore Ts'o , Dominik Brodowski , Russell King , Catalin Marinas , Will Deacon , Geert Uytterhoeven , Thomas Bogendoerfer , Paul Walmsley , Palmer Dabbelt , Albert Ou , "David S . Miller" , Richard Weinberger , Anton Ivanov , Ingo Molnar , Borislav Petkov , Dave Hansen , "H . Peter Anvin" , Chris Zankel , Max Filippov , Stephen Boyd , Dinh Nguyen , linux-arm-kernel@lists.infradead.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-riscv@lists.infradead.org, sparclinux@vger.kernel.org, linux-um@lists.infradead.org, x86@kernel.org, linux-xtensa@linux-xtensa.org Date: Tue, 19 Apr 2022 13:33:21 +0200 In-Reply-To: <20220419111650.1582274-9-Jason@zx2c4.com> References: <20220419111650.1582274-1-Jason@zx2c4.com> <20220419111650.1582274-9-Jason@zx2c4.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.42.4 (3.42.4-2.fc35) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-malware-bazaar: not-scanned Precedence: bulk List-ID: X-Mailing-List: linux-crypto@vger.kernel.org On Tue, 2022-04-19 at 13:16 +0200, Jason A. Donenfeld wrote: > In the event that random_get_entropy() can't access a cycle counter or > similar, falling back to returning 0 is really not the best we can do. > Instead, at least calling random_get_entropy_fallback() would be > preferable, because that always needs to return _something_, even > falling back to jiffies eventually. It's not as though > random_get_entropy_fallback() is super high precision or guaranteed to > be entropic, but basically anything that's not zero all the time is > better than returning zero all the time. > > This is accomplished by just including the asm-generic code like on > other architectures, which means we can get rid of the empty stub > function here. LGTM, actually better than before, though not even sure any drivers in ARCH=um have interrupts that say they can be used for this. Acked-by: Johannes Berg I assume you're going to take this through the random tree? johannes