Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754585AbeAJN7K (ORCPT + 1 other); Wed, 10 Jan 2018 08:59:10 -0500 Received: from twosheds.infradead.org ([90.155.92.209]:49684 "EHLO twosheds.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751884AbeAJN7J (ORCPT ); Wed, 10 Jan 2018 08:59:09 -0500 Message-ID: <1515592736.22302.167.camel@infradead.org> Subject: Re: [patch RFC 5/5] x86/speculation: Add basic speculation control code From: David Woodhouse To: Thomas Gleixner Cc: Andrea Arcangeli , Jiri Kosina , "asit.k.mallick" , "Van De Ven, Arjan" , Peter Zijlstra , Dave Hansen , LKML , Linus Torvalds , x86@kernel.org, Borislav Petkov , Tim Chen , Andi Kleen , Greg KH , Andy Lutomirski In-Reply-To: References: <20180110092234.GY29822@worktop.programming.kicks-ass.net> <1515576479.22302.81.camel@infradead.org> <20180110115419.GA9706@redhat.com> <1515585534.22302.122.camel@infradead.org> <20180110120158.GB9706@redhat.com> <1515586174.22302.126.camel@infradead.org> <20180110121755.GD9706@redhat.com> <1515587384.22302.132.camel@infradead.org> <20180110124119.GG9706@redhat.com> <20180110125710.GH9706@redhat.com> <1515589641.22302.145.camel@infradead.org> Face: 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 Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-DNIz9A5OXkzTihaybYAn" Date: Wed, 10 Jan 2018 13:58:56 +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 Return-Path: --=-DNIz9A5OXkzTihaybYAn Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2018-01-10 at 14:46 +0100, Thomas Gleixner wrote: >=20 > So here is the simple list of questions all to be answered with YES or > NO. I don't want to see any of the 'but, though ...'. We all know by now > that it's CPU dependent and slow and whatever and that IBRS_ATT will be i= n > future CPUs. So get your act together and tell a clear YES or NO. This is actually covered by the documentation. Someone really should send you a copy. > 1) Does IBRS=3D1 when set once act as a set-and-forget option ? Never on current hardware. In future with IBRS_ATT, yes. > =C2=A01a) If the answer to #1 is yes, is it more secure than toggling it? No, just faster. > =C2=A01b) If the answer to #1 is yes, is retpoline required ? No. We'll ALTERNATIVE it away if we have IBRS_ATT. > =C2=A01c) If the answer to #1 is yes, is RSB stuffing required ? Not for IBRS_ATT, with weasel words about requiring SMEP. > 2) Does toggle mode of IBRS require retpoline ? No. Retpoline is an *alternative* to IBRS, for protecting the kernel. > 3) Does toggle mode of IBRS require RSB stuffing ? Yes for kernel entry if you have no SMEP. And yes on vmexit. > 4) Exist CPUs which require IBRS to be selected automatically ? >=20 > =C2=A0=C2=A0 4b) If yes, provide the list as a separate answer please You mean CPUs on which retpoline isn't sufficient and thus the =C2=A0kernel should prefer IBRS "automatically" without a command line option? As discussed, yes on Skylake and anything after it that doesn't have IBRS_ATT, because there are tiny theoretical gaps that retpoline doesn't handle. But the option of sacrificing goats may be perfectly acceptable. --=-DNIz9A5OXkzTihaybYAn 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 3PZ0chY1PaVWjg59d4Uno+5LRDbgCnPkKJX4ysBGadibjBGQGJEZCjh94iiEebn2KsRLvtrJ72Ph 3W2HDEdngW3YP0wujFQVs81U7L8XN3kdPRsa9zNqGtYQP/+1KMMJQ57hnfi9AgMBAAGjggHpMIIB 5TAfBgNVHSMEGDAWgBSCr2yM+MX+lmF86B89K3FIXsSLwDAdBgNVHQ4EFgQUpL+/5lli9jmj2KHj ryyhnB2xRt0wDgYDVR0PAQH/BAQDAgWgMAwGA1UdEwEB/wQCMAAwIAYDVR0lBBkwFwYIKwYBBQUH AwQGCysGAQQBsjEBAwUCMBEGCWCGSAGG+EIBAQQEAwIFIDBGBgNVHSAEPzA9MDsGDCsGAQQBsjEB AgEBATArMCkGCCsGAQUFBwIBFh1odHRwczovL3NlY3VyZS5jb21vZG8ubmV0L0NQUzBaBgNVHR8E UzBRME+gTaBLhklodHRwOi8vY3JsLmNvbW9kb2NhLmNvbS9DT01PRE9SU0FDbGllbnRBdXRoZW50 aWNhdGlvbmFuZFNlY3VyZUVtYWlsQ0EuY3JsMIGLBggrBgEFBQcBAQR/MH0wVQYIKwYBBQUHMAKG SWh0dHA6Ly9jcnQuY29tb2RvY2EuY29tL0NPTU9ET1JTQUNsaWVudEF1dGhlbnRpY2F0aW9uYW5k U2VjdXJlRW1haWxDQS5jcnQwJAYIKwYBBQUHMAGGGGh0dHA6Ly9vY3NwLmNvbW9kb2NhLmNvbTAe BgNVHREEFzAVgRNkd213MkBpbmZyYWRlYWQub3JnMA0GCSqGSIb3DQEBCwUAA4IBAQCK28BdbVJ9 QKQqTDfXwogAYiRBEGptfE1Bjy4F5vC6eWJqOJ15vunxjLwdbZYb4L0qrJlh+ZHHHlbIK8uEZu7N XHUntmWMbGbZiu7JgrbSXJK1ct9gxrN/sdWYJ+JDjVHg7GfDTvTTPa26JMRqJsO1TjjyDX7A3K39 TjV8C0hqXvwF9BsNf+qBeWO6GVzJ5572awY221hc1umibmZaKV4fg+7fS7qscx5TSuIc6uvMBQhm 7NQiCq6euMMWBDUDlotQCDW0ilm0OuLW3IVLuZCm6Msc+6hT9+dCT4JUvxTHZnnO7uLCxV+Ujad+ PH3itRm38i96p2zvwgLr8vwWA0ckMIIFMTCCBBmgAwIBAgIQTUYRMpPx2e52jnkx1q87gDANBgkq hkiG9w0BAQsFADCBlzELMAkGA1UEBhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQ MA4GA1UEBxMHU2FsZm9yZDEaMBgGA1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENP TU9ETyBSU0EgQ2xpZW50IEF1dGhlbnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTcx MjIxMDAwMDAwWhcNMTgxMjIxMjM1OTU5WjAkMSIwIAYJKoZIhvcNAQkBFhNkd213MkBpbmZyYWRl YWQub3JnMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA4MyzVmtfAzaRlI/2Xh9EoM+d xEiG83T8NziXrjT+o2YcWaI28n8WzIRE7HMSPx4+lGeGu7B5uQZFY5bAdQH9mWvz11LfDJiwHDzB 5DDxrp75FImxL25Q76ajJEGZWmTPreT6hZlpG3oS2hL26TWO3ZhAAHioeJJU8yc66+QAM2gkN9nA Nnt/gxCL+TuZfVYjCI8vyTPsTEK319z2dHIWNT2lVo4OfXeFJ6PuS0Q24Apz5CiV+MrARmnYm4wR kBiRGQo4feIohHm59irES77aye9j4d1thwxHZ4Ft2D9MLoxUFbPNVOy/Fzd5HT0bGvczahrWED// tSjDCUOe4Z34vQIDAQABo4IB6TCCAeUwHwYDVR0jBBgwFoAUgq9sjPjF/pZhfOgfPStxSF7Ei8Aw HQYDVR0OBBYEFKS/v+ZZYvY5o9ih468soZwdsUbdMA4GA1UdDwEB/wQEAwIFoDAMBgNVHRMBAf8E AjAAMCAGA1UdJQQZMBcGCCsGAQUFBwMEBgsrBgEEAbIxAQMFAjARBglghkgBhvhCAQEEBAMCBSAw RgYDVR0gBD8wPTA7BgwrBgEEAbIxAQIBAQEwKzApBggrBgEFBQcCARYdaHR0cHM6Ly9zZWN1cmUu Y29tb2RvLm5ldC9DUFMwWgYDVR0fBFMwUTBPoE2gS4ZJaHR0cDovL2NybC5jb21vZG9jYS5jb20v Q09NT0RPUlNBQ2xpZW50QXV0aGVudGljYXRpb25hbmRTZWN1cmVFbWFpbENBLmNybDCBiwYIKwYB BQUHAQEEfzB9MFUGCCsGAQUFBzAChklodHRwOi8vY3J0LmNvbW9kb2NhLmNvbS9DT01PRE9SU0FD bGllbnRBdXRoZW50aWNhdGlvbmFuZFNlY3VyZUVtYWlsQ0EuY3J0MCQGCCsGAQUFBzABhhhodHRw Oi8vb2NzcC5jb21vZG9jYS5jb20wHgYDVR0RBBcwFYETZHdtdzJAaW5mcmFkZWFkLm9yZzANBgkq hkiG9w0BAQsFAAOCAQEAitvAXW1SfUCkKkw318KIAGIkQRBqbXxNQY8uBebwunliajideb7p8Yy8 HW2WG+C9KqyZYfmRxx5WyCvLhGbuzVx1J7ZljGxm2YruyYK20lyStXLfYMazf7HVmCfiQ41R4Oxn w0700z2tuiTEaibDtU448g1+wNyt/U41fAtIal78BfQbDX/qgXljuhlcyeee9msGNttYXNbpom5m WileH4Pu30u6rHMeU0riHOrrzAUIZuzUIgqunrjDFgQ1A5aLUAg1tIpZtDri1tyFS7mQpujLHPuo U/fnQk+CVL8Ux2Z5zu7iwsVflI2nfjx94rUZt/Iveqds78IC6/L8FgNHJDCCBeYwggPOoAMCAQIC EGqb4Tg7/ytrnwHV2binUlYwDQYJKoZIhvcNAQEMBQAwgYUxCzAJBgNVBAYTAkdCMRswGQYDVQQI ExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBD QSBMaW1pdGVkMSswKQYDVQQDEyJDT01PRE8gUlNBIENlcnRpZmljYXRpb24gQXV0aG9yaXR5MB4X DTEzMDExMDAwMDAwMFoXDTI4MDEwOTIzNTk1OVowgZcxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJH cmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBM aW1pdGVkMT0wOwYDVQQDEzRDT01PRE8gUlNBIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQgU2Vj dXJlIEVtYWlsIENBMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAvrOeV6wodnVAFsc4 A5jTxhh2IVDzJXkLTLWg0X06WD6cpzEup/Y0dtmEatrQPTRI5Or1u6zf+bGBSyD9aH95dDSmeny1 nxdlYCeXIoymMv6pQHJGNcIDpFDIMypVpVSRsivlJTRENf+RKwrB6vcfWlP8dSsE3Rfywq09N0Zf xcBa39V0wsGtkGWC+eQKiz4pBZYKjrc5NOpG9qrxpZxyb4o4yNNwTqzaaPpGRqXB7IMjtf7tTmU2 jqPMLxFNe1VXj9XB1rHvbRikw8lBoNoSWY66nJN/VCJv5ym6Q0mdCbDKCMPybTjoNCQuelc0IAaO 4nLUXk0BOSxSxt8kCvsUtQIDAQABo4IBPDCCATgwHwYDVR0jBBgwFoAUu69+Aj36pvE8hI6t7jiY 7NkyMtQwHQYDVR0OBBYEFIKvbIz4xf6WYXzoHz0rcUhexIvAMA4GA1UdDwEB/wQEAwIBhjASBgNV HRMBAf8ECDAGAQH/AgEAMBEGA1UdIAQKMAgwBgYEVR0gADBMBgNVHR8ERTBDMEGgP6A9hjtodHRw Oi8vY3JsLmNvbW9kb2NhLmNvbS9DT01PRE9SU0FDZXJ0aWZpY2F0aW9uQXV0aG9yaXR5LmNybDBx BggrBgEFBQcBAQRlMGMwOwYIKwYBBQUHMAKGL2h0dHA6Ly9jcnQuY29tb2RvY2EuY29tL0NPTU9E T1JTQUFkZFRydXN0Q0EuY3J0MCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5jb21vZG9jYS5jb20w DQYJKoZIhvcNAQEMBQADggIBAHhcsoEoNE887l9Wzp+XVuyPomsX9vP2SQgG1NgvNc3fQP7TcePo 7EIMERoh42awGGsma65u/ITse2hKZHzT0CBxhuhb6txM1n/y78e/4ZOs0j8CGpfb+SJA3GaBQ+39 4k+z3ZByWPQedXLL1OdK8aRINTsjk/H5Ns77zwbjOKkDamxlpZ4TKSDMKVmU/PUWNMKSTvtlenlx Bhh7ETrN543j/Q6qqgCWgWuMAXijnRglp9fyadqGOncjZjaaSOGTTFB+E2pvOUtY+hPebuPtTbq7 vODqzCM6ryEhNhzf+enm0zlpXK7q332nXttNtjv7VFNYG+I31gnMrwfHM5tdhYF/8v5UY5g2xANP ECTQdu9vWPoqNSGDt87b3gXb1AiGGaI06vzgkejL580ul+9hz9D0S0U4jkhJiA7EuTecP/CFtR72 uYRBcunwwH3fciPjviDDAI9SnC/2aPY8ydehzuZutLbZdRJ5PDEJM/1tyZR2niOYihZ+FCbtf3D9 mB12D4ln9icgc7CwaxpNSCPt8i/GqK2HsOgkL3VYnwtx7cJUmpvVdZ4ognzgXtgtdk3ShrtOS1iA N2ZBXFiRmjVzmehoMof06r1xub+85hFQzVxZx5/bRaTKTlL8YXLI8nAbR9HWdFqzcOoB/hxfEyIQ px9/s81rgzdEZOofSlZHynoSMYIDxzCCA8MCAQEwgawwgZcxCzAJBgNVBAYTAkdCMRswGQYDVQQI ExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBD QSBMaW1pdGVkMT0wOwYDVQQDEzRDT01PRE8gUlNBIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQg U2VjdXJlIEVtYWlsIENBAhBNRhEyk/HZ7naOeTHWrzuAMA0GCWCGSAFlAwQCAQUAoIIB6zAYBgkq hkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xODAxMTAxMzU4NTZaMC8GCSqG SIb3DQEJBDEiBCBt3BdZxvllJL6v9i0zIawHEjcC3VbtMbRGMwTIlj+zsDCBvQYJKwYBBAGCNxAE MYGvMIGsMIGXMQswCQYDVQQGEwJHQjEbMBkGA1UECBMSR3JlYXRlciBNYW5jaGVzdGVyMRAwDgYD VQQHEwdTYWxmb3JkMRowGAYDVQQKExFDT01PRE8gQ0EgTGltaXRlZDE9MDsGA1UEAxM0Q09NT0RP IFJTQSBDbGllbnQgQXV0aGVudGljYXRpb24gYW5kIFNlY3VyZSBFbWFpbCBDQQIQTUYRMpPx2e52 jnkx1q87gDCBvwYLKoZIhvcNAQkQAgsxga+ggawwgZcxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJH cmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBM aW1pdGVkMT0wOwYDVQQDEzRDT01PRE8gUlNBIENsaWVudCBBdXRoZW50aWNhdGlvbiBhbmQgU2Vj dXJlIEVtYWlsIENBAhBNRhEyk/HZ7naOeTHWrzuAMA0GCSqGSIb3DQEBAQUABIIBAJ2Rs7WvpGVA Gxau6Lu+FrM3KdZ9lAgwxp8ON2UbGZt4dkj9K5KFB2evGh63At0nM2ygo+tgo/1JDGqa+7JQhUy7 nEXGKwuAERk+15kSUCH8khf45DBubvHBTANgjPL0qXtDBRmRFiC7LcZpXSQPIdv15WlvYR79pcte VvpD2Lkx9YwrPnTJz7Y8lIe8LYHj28a4CZy5KG1ZCx6jKb5fdLQvYjHcfkKozxD0fVcSQuWZbG+2 D3zb0zCd4IqO9T4OdfVT7u6jsGcsXNPlXmi5uv5DLUGwaRXWCK36utjCcc2wiVR/ouyOWgEdP4gw 5CfWynrA2bpX0S4bIGe0HGuoWmEAAAAAAAA= --=-DNIz9A5OXkzTihaybYAn--