From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Woodhouse, David" Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation Date: Tue, 23 Jan 2018 23:14:36 +0000 Message-ID: <1516749276.13558.25.camel@amazon.co.uk> References: <1516476182-5153-1-git-send-email-karahmed@amazon.de> <1516476182-5153-10-git-send-email-karahmed@amazon.de> <243BE571-AF73-44B3-8D17-193F9E07686A@amacapital.net> <4e01a7a9-29e4-adcc-3f53-550fb7f3d370@amd.com> <1516724457.9521.156.camel@amazon.co.uk> <20180123224956.GQ7844@tassilo.jf.intel.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=sha-256; protocol="application/x-pkcs7-signature"; boundary="=-q+mZOhcj9cJaZ9CQ8Sfx" Cc: Andy Lutomirski , KarimAllah Ahmed , , Andrea Arcangeli , Andy Lutomirski , Arjan van de Ven , Ashok Raj , Asit Mallick , Borislav Petkov , Dan Williams , Dave Hansen , "Greg Kroah-Hartman" , "H . Peter Anvin" , Ingo Molnar , Janakarajan Natarajan , Joerg Roedel , "Jun Nakajima" , Laura Abbott , "Linus Torvalds" , Masami Hiram To: Andi Kleen , Tom Lendacky Return-path: In-Reply-To: <20180123224956.GQ7844@tassilo.jf.intel.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org --=-q+mZOhcj9cJaZ9CQ8Sfx Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2018-01-23 at 14:49 -0800, Andi Kleen wrote: > > Not sure.=C2=A0 Maybe to start, the answer might be to allow it to be s= et for > > the ultra-paranoid, but in general don't enable it by default.=C2=A0 Ha= ving it > > enabled would be an alternative to someone deciding to disable SMT, sin= ce > > that would have even more of a performance impact. >=20 > I agree. A reasonable strategy would be to only enable it for > processes that have dumpable disabled. This should be already set for > high value processes like GPG, and allows others to opt-in if > they need to. That seems to make sense, and I think was the solution we were approaching for IBPB on context switch too, right? Are we generally agreed on dumpable as the criterion for both of those? --=-q+mZOhcj9cJaZ9CQ8Sfx 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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