From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752348AbeBSJo3 (ORCPT ); Mon, 19 Feb 2018 04:44:29 -0500 Received: from twosheds.infradead.org ([90.155.92.209]:40394 "EHLO twosheds.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752295AbeBSJo2 (ORCPT ); Mon, 19 Feb 2018 04:44:28 -0500 Message-ID: <1519033461.7876.58.camel@infradead.org> Subject: Re: [tip:x86/pti] x86/speculation: Use IBRS if available before calling into firmware From: David Woodhouse To: Ingo Molnar Cc: Peter Zijlstra , Tim Chen , hpa@zytor.com, tglx@linutronix.de, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, linux-tip-commits@vger.kernel.org, Borislav Petkov In-Reply-To: <20180219093927.644jb6h5peworj62@gmail.com> References: <1518362359-1005-1-git-send-email-dwmw@amazon.co.uk> <1518808600.7876.49.camel@infradead.org> <66f94cb1-8160-56e0-680c-2e847ae05893@linux.intel.com> <20180217102616.vcwatxsgj2vunlew@gmail.com> <20180219092017.GN25201@hirez.programming.kicks-ass.net> <1519032552.7876.55.camel@infradead.org> <20180219093927.644jb6h5peworj62@gmail.com> Face: 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 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-Zhq5tQaEuTYR8n4T5ISh" Date: Mon, 19 Feb 2018 09:44:21 +0000 Mime-Version: 1.0 X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 X-SRS-Rewrite: SMTP reverse-path rewritten from by twosheds.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-Zhq5tQaEuTYR8n4T5ISh Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2018-02-19 at 10:39 +0100, Ingo Molnar wrote: > * David Woodhouse wrote: >=20 > >=20 > > On Mon, 2018-02-19 at 10:20 +0100, Peter Zijlstra wrote: > > >=20 > > >=20 > > > I did not update or otherwise change packages while I was bisecting; = the > > > machine is: > > >=20 > > > vendor_id=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : GenuineIntel > > > cpu family=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : 6 > > > model=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : 6= 2 > > > model name=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : Intel(R) Xeon(R) CPU E5-26= 80 v2 @ 2.80GHz > > > stepping=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : 4 > > > microcode=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 : 0x428 > > That's IVX with a microcode that doesn't *have* IBRS/IBPB. I don't > > think there's a publicly available microcode that does; I assume you > > didn't have one and build it into your kernel for early loading, and > > thus you really weren't even using IBRS here? The code never even gets > > patched in? > Note that PeterZ's boot troubles only match the *symptoms* of the spuriou= s=C2=A0 > failures reported by Tim Chen. Your commit wasn't bisected to. >=20 > I linked these two reports on the (remote) possibility that they might be= related=C2=A0 > via some alignment dependent bug somewhere else in the x86 kernel - possi= bly=C2=A0 > completely unrelated to any IBRS/IBPB details. Understood. I was merely *accentuating* the "completely unrelated to any IBRS/IBPB" bit, in a "la la la I'm ignoring this because I'm working on other things" kind of a way... :) --=-Zhq5tQaEuTYR8n4T5ISh Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEFQw ggUxMIIEGaADAgECAhBNRhEyk/HZ7naOeTHWrzuAMA0GCSqGSIb3DQEBCwUAMIGXMQswCQYDVQQG EwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYDVQQHEwdTYWxmb3JkMRowGAYD VQQKExFDT01PRE8gQ0EgTGltaXRlZDE9MDsGA1UEAxM0Q09NT0RPIFJTQSBDbGllbnQgQXV0aGVu dGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQTAeFw0xNzEyMjEwMDAwMDBaFw0xODEyMjEyMzU5 NTlaMCQxIjAgBgkqhkiG9w0BCQEWE2R3bXcyQGluZnJhZGVhZC5vcmcwggEiMA0GCSqGSIb3DQEB AQUAA4IBDwAwggEKAoIBAQDgzLNWa18DNpGUj/ZeH0Sgz53ESIbzdPw3OJeuNP6jZhxZojbyfxbM hETscxI/Hj6UZ4a7sHm5BkVjlsB1Af2Za/PXUt8MmLAcPMHkMPGunvkUibEvblDvpqMkQZlaZM+t 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