From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.7 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 775977D2F0 for ; Wed, 28 Aug 2019 10:31:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726508AbfH1KbR (ORCPT ); Wed, 28 Aug 2019 06:31:17 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:48064 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726395AbfH1KbQ (ORCPT ); Wed, 28 Aug 2019 06:31:16 -0400 Received: by atrey.karlin.mff.cuni.cz (Postfix, from userid 512) id BBF1F81097; Wed, 28 Aug 2019 12:31:00 +0200 (CEST) Date: Wed, 28 Aug 2019 12:31:13 +0200 From: Pavel Machek To: Thomas Gleixner Cc: Pavel Machek , Greg Kroah-Hartman , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Tom Lendacky , Borislav Petkov , Andrew Cooper , Andrew Morton , Chen Yu , "H. Peter Anvin" , Ingo Molnar , Jonathan Corbet , Josh Poimboeuf , Juergen Gross , Kees Cook , "linux-doc@vger.kernel.org" , "linux-pm@vger.kernel.org" , Nathan Chancellor , Paolo Bonzini , "Rafael J. Wysocki" , "x86@kernel.org" Subject: Re: [PATCH 4.19 72/98] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h Message-ID: <20190828103113.GA14677@amd> References: <20190827072718.142728620@linuxfoundation.org> <20190827072722.020603090@linuxfoundation.org> <20190827113604.GB18218@amd> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="ikeVEW9yuYc//A+q" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --ikeVEW9yuYc//A+q Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue 2019-08-27 15:30:30, Thomas Gleixner wrote: > On Tue, 27 Aug 2019, Pavel Machek wrote: >=20 > > On Tue 2019-08-27 09:50:51, Greg Kroah-Hartman wrote: > > > From: Tom Lendacky > > >=20 > > > commit c49a0a80137c7ca7d6ced4c812c9e07a949f6f24 upstream. > > >=20 > > > There have been reports of RDRAND issues after resuming from suspend = on > > > some AMD family 15h and family 16h systems. This issue stems from a B= IOS > > > not performing the proper steps during resume to ensure RDRAND contin= ues > > > to function properly. > >=20 > > Yes. And instead of reinitializing the RDRAND on resume, this patch > > breaks support even for people with properly functioning BIOSes... >=20 > There is no way to reinitialize RDRAND from the kernel otherwise we would > have exactly done that. If you know how to do that please tell. Would they? AMD is not exactly doing good job with communication here. If BIOS can do it, kernel can do it, too... or do you have information saying otherwise? > Also disabling it for every BIOS is the only way which can be done because > there is no way to know whether the BIOS is fixed or not at cold boot > time. And it has to be known there because applications cache the I'm pretty sure DMI-based whitelist would help here. It should be reasonably to fill it with the common machines at least. Plus, where is the CVE, and does AMD do anything to make BIOS vendors fix them? Best regards, Pavel --=20 DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany --ikeVEW9yuYc//A+q Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl1mV/EACgkQMOfwapXb+vKEEACfa9KYDavWYmga5YIPImafscUZ 6ToAoKvc4xitFnoM3ETkUUD2cV1in6+x =OTpt -----END PGP SIGNATURE----- --ikeVEW9yuYc//A+q--