Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752101AbeAOSII (ORCPT + 1 other); Mon, 15 Jan 2018 13:08:08 -0500 Received: from twosheds.infradead.org ([90.155.92.209]:42860 "EHLO twosheds.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbeAOSIG (ORCPT ); Mon, 15 Jan 2018 13:08:06 -0500 Message-ID: <1516039672.4937.13.camel@infradead.org> Subject: Re: Improve retpoline for Skylake From: David Woodhouse To: Andy Lutomirski , Andrew Cooper Cc: Jon Masters , Henrique de Moraes Holschuh , Andi Kleen , tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, pjt@google.com, torvalds@linux-foundation.org, gregkh@linux-foundation.org, peterz@infradead.org, thomas.lendacky@amd.com, arjan.van.de.ven@intel.com In-Reply-To: References: <20180112184550.6573-1-andi@firstfloor.org> <1515784373.22302.492.camel@infradead.org> <20180112192126.su2evwfefdfeaa6g@two.firstfloor.org> <20180112220349.7dorb3lde4tffsjm@khazad-dum.debian.net> <985f979e-0740-5d8a-d6b8-b023105aa021@jonmasters.org> <445ec6c6-a835-fbdc-dca3-222a73d19816@citrix.com> Face: 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 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-h9fhweBmwq0T76V026wS" Date: Mon, 15 Jan 2018 19:07:52 +0100 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 Return-Path: --=-h9fhweBmwq0T76V026wS Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2018-01-15 at 10:06 -0800, Andy Lutomirski wrote: >=20 > > Refill or not, you are aware that a correctly timed SMI in a leaf > > function will cause the next ret to speculate into userspace, because > > there is guaranteed peturbance in the RSB?=C2=A0 (On the expectation th= at the > > SMM handler isn't entirely devoid of function calls). >=20 > Couldn't firmware fill=C2=A0the RSB with a some known safe address, maybe > even 0, and then immediately do RSM? Why don't we just unconditionally declare that *all* firmware that uses SMI for anything at all is broken? --=-h9fhweBmwq0T76V026wS 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 5PqFmWkbehLaEvbpNY7dmEAAeKh4klTzJzrr5AAzaCQ32cA2e3+DEIv5O5l9ViMIjy/JM+xMQrfX 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