From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELt2RzpC7CLGrcVOmVlNZmDq9YXIvOB6mc+IugXV+PI1cp6ppNFnQ4uhH5o6J0vBPMPZBQg7 ARC-Seal: i=1; a=rsa-sha256; t=1520077084; cv=none; d=google.com; s=arc-20160816; b=sPdyeNUC/HX60qe/FABAFqUwOy43tqJAdFwE7242Bbc6lw1OCxNJZUbNtU+PiZt7WT 8qAOVwLSn7eVxc1fi0K1Sil7M7AAIt6KRNTBXmN9DepGGfMJpg+D0bjTTrutrGAEE6jZ 1+WkSY6pWTUw9Oy25u37iSNO82fs7Bp6Qv4fVkygi8lnljrIFe86c2sQssiIB+jfAijO 4FPrjQF8l7Uj91lxvHpDGBKqaKzgitppbHL7an6YP1BkJrL7waLfXdaqKELCJzEWIOzB AtPWN0DBV3jJ4y1ShuWDiUaSMWks88M/7dPNpZCzi3cLkSbKxX0zuimDViEWoX1WJ0bB S/vA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=precedence:mime-version:accept-language:in-reply-to:references :message-id:date:thread-index:thread-topic:subject:cc:to:from :mime-version:dkim-signature:arc-authentication-results; bh=As9IY5rHXV5vmlNAt6Tb0sJ0mAl0tnt9jiTDWqf1gvU=; b=G3W0/VcKxMaQvpZnMNbqaQtD6wZM970QVAK0g4u1oKH3rtftHpK1zhu924m7nmLaj0 G+1nJrUyA9+j9BzjHQ/g3xyHGQq6Z2elyqB+7o+D22W4ZMMWd84di1P0jz/veqA66qU7 xqOHq81BnQpxrl36AaXubGmwcZ3mPVmdutpJAFGFjTuyWF1LH8GhhyAgKQ4XfFHDggkx R4u/QuQaCyEvvRGxqF6kkbadpFXXckBbzlYmrFLUsK2pC3KJatCGLkRoRaFQMUgg48jE +MtYOFAvMZRz/5pP+MK87E5kET469BT9L+cg6ALzHbixqEkzilygEp0L9wve+hIL4ter hDsQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@amazon.co.uk header.s=amazon201209 header.b=MZtrH7he; spf=pass (google.com: domain of prvs=593727dcc=dwmw@amazon.co.uk designates 72.21.198.25 as permitted sender) smtp.mailfrom=prvs=593727dcc=dwmw@amazon.co.uk; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=amazon.co.uk Authentication-Results: mx.google.com; dkim=pass header.i=@amazon.co.uk header.s=amazon201209 header.b=MZtrH7he; spf=pass (google.com: domain of prvs=593727dcc=dwmw@amazon.co.uk designates 72.21.198.25 as permitted sender) smtp.mailfrom=prvs=593727dcc=dwmw@amazon.co.uk; dmarc=pass (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=amazon.co.uk X-Amazon-filename: smime.p7s X-IronPort-AV: E=Sophos;i="5.47,417,1515456000"; d="p7s'?scan'208";a="710276917" Content-Type: multipart/mixed; boundary="===============7353256177094947470==" MIME-Version: 1.0 From: "Woodhouse, David" To: "gregkh@linuxfoundation.org" , "tim.c.chen@linux.intel.com" CC: "mingo@kernel.org" , "peterz@infradead.org" , "arjan@linux.intel.com" , "Raslan, KarimAllah" , "torvalds@linux-foundation.org" , "tglx@linutronix.de" , "linux-mm@kvack.org" , "nadav.amit@gmail.com" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "ak@linux.intel.com" , "akpm@linux-foundation.org" , "riel@redhat.com" , "luto@kernel.org" , "pbonzini@redhat.com" , "bp@alien8.de" , "dave.hansen@intel.com" , "mgorman@suse.de" Subject: Re: [PATCH 0/2] Backport IBPB on context switch to non-dumpable process Thread-Topic: [PATCH 0/2] Backport IBPB on context switch to non-dumpable process Thread-Index: AQHTss1QN1m3UrzBOUaJwGMCvDXcRaO+YomA Date: Sat, 3 Mar 2018 11:37:56 +0000 Message-ID: <1520077075.7929.4.camel@amazon.co.uk> References: <20180303085454.GA23988@kroah.com> In-Reply-To: <20180303085454.GA23988@kroah.com> Accept-Language: en-GB, en-US X-MS-Has-Attach: yes X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.43.61.91] MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1593863143306630762?= X-GMAIL-MSGID: =?utf-8?q?1593916348880823953?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: --===============7353256177094947470== Content-Language: en-US Content-Type: multipart/signed; micalg=sha-256; protocol="application/x-pkcs7-signature"; boundary="=-Z7kEP2drWRt5Nh7dR/J8" --=-Z7kEP2drWRt5Nh7dR/J8 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, 2018-03-03 at 09:54 +0100, Greg Kroah-Hartman wrote: > On Fri, Mar 02, 2018 at 01:32:08PM -0800, Tim Chen wrote: > >=20 > > Greg, > >=20 > > I will like to propose backporting "x86/speculation: Use Indirect Branc= h > > Prediction Barrier on context switch" from commit 18bf3c3e in upstream > > to 4.9 and 4.4 stable.=C2=A0=C2=A0The patch has already been ported to = 4.14 and > > 4.15 stable.=C2=A0=C2=A0The patch needs mm context id that Andy added i= n commit > > f39681ed. I have lifted the mm context id change from Andy's upstream > > patch and included it here. > > What does this patch "fix" in those older kernels?=C2=A0=C2=A0Is this a > performance improvement or something else? It's part of the Spectre variant 2 mitigation =E2=80=94 a full flush of the branch prediction on context switch to a sensitive=C2=B9 process. It was th= e one I called out as "needs more attention" when I did the rest of the retpoline etc backportingk, and Tim has now fixed it up. (Thanks). =C2=B9 for now, "sensitive" means non-dumpable. This isn't perfect but it's a reasonable approximation for now; it would be too expensive to do it on *every* context switch. And for your purposes, the important part is that it's what's upstream. --=-Z7kEP2drWRt5Nh7dR/J8 Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCEE4w ggUuMIIEFqADAgECAhEApEtL31g6H7ROXdOiQnA9RjANBgkqhkiG9w0BAQsFADCBlzELMAkGA1UE BhMCR0IxGzAZBgNVBAgTEkdyZWF0ZXIgTWFuY2hlc3RlcjEQMA4GA1UEBxMHU2FsZm9yZDEaMBgG A1UEChMRQ09NT0RPIENBIExpbWl0ZWQxPTA7BgNVBAMTNENPTU9ETyBSU0EgQ2xpZW50IEF1dGhl bnRpY2F0aW9uIGFuZCBTZWN1cmUgRW1haWwgQ0EwHhcNMTcxMjIxMDAwMDAwWhcNMTgxMjIxMjM1 OTU5WjAiMSAwHgYJKoZIhvcNAQkBFhFkd213QGFtYXpvbi5jby51azCCASIwDQYJKoZIhvcNAQEB BQADggEPADCCAQoCggEBAKdGKgXuwKMg2r+i/4BZZC0ddRxNq3xIKTakie/VCSzoO7P17A36ZzUc VMEYPfqDt/65xoc6Tdih+qkY2pNDppZ1DZ8mVrAX6O2O60ZhmXB60wMoDvXPZInvkMOW4drqnje/ 7/NOypn/XQAY+ln4KT+3tHG3TfryyJFMedqC/r29KJlCeeCxIzdtq2j5mN42tvPVv4+p+Kr77uui 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