From: Gary R Hook Subject: Re: Poor RNG performance on Ryzen Date: Fri, 21 Jul 2017 10:04:16 -0500 Message-ID: <842a138e-ff8f-4a2a-0bbe-3e419b008d65@amd.com> References: <1218e9b7-4eeb-d8a0-02b2-8ddd672ec454@gmail.com> <20170721092656.GA18604@wintermute> <09c9be2b-8b4d-ee06-8071-4f748fdb5970@gmail.com> <20170721144741.4igkvsd2fowptsy2@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "linux-crypto@vger.kernel.org" To: Theodore Ts'o , Oliver Mangold Return-path: Received: from mail-bl2nam02on0068.outbound.protection.outlook.com ([104.47.38.68]:25376 "EHLO NAM02-BL2-obe.outbound.protection.outlook.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750849AbdGUPEv (ORCPT ); Fri, 21 Jul 2017 11:04:51 -0400 In-Reply-To: <20170721144741.4igkvsd2fowptsy2@thunk.org> Sender: linux-crypto-owner@vger.kernel.org List-ID: On 07/21/2017 09:47 AM, Theodore Ts'o wrote: > On Fri, Jul 21, 2017 at 01:39:13PM +0200, Oliver Mangold wrote: >> Better, but obviously there is still much room for improvement by reducing >> the number of calls to RDRAND. > > Hmm, is there some way we can easily tell we are running on Ryzen? Or > do we believe this is going to be true for all AMD devices? > > I guess we could add some kind of "has_crappy_arch_get_random()" call > which could be defined by arch/x86, and change how aggressively we use > arch_get_random_*() depending on whether has_crappy_arch_get_random() > returns true or not.... Just a quick note to say that we are aware of the issue, and that it is being addressed.