Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755950AbeAHIhL (ORCPT + 1 other); Mon, 8 Jan 2018 03:37:11 -0500 Received: from smtp-fw-9102.amazon.com ([207.171.184.29]:34570 "EHLO smtp-fw-9102.amazon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755009AbeAHIhJ (ORCPT ); Mon, 8 Jan 2018 03:37:09 -0500 X-Amazon-filename: smime.p7s X-IronPort-AV: E=Sophos;i="5.46,330,1511827200"; d="p7s'?scan'208";a="584797839" Message-ID: <1515398120.7317.4.camel@amazon.co.uk> Subject: Re: [PATCH v3 01/13] x86/retpoline: Add initial retpoline support To: Josh Poimboeuf , Borislav Petkov CC: "tglx@linutronix.de" , "linux-kernel@vger.kernel.org" , "tim.c.chen@linux.intel.com" , "peterz@infradead.org" , "torvalds@linux-foundation.org" , "ak@linux.intel.com" , "riel@redhat.com" , "keescook@google.com" , "gnomes@lxorguk.ukuu.org.uk" , "pjt@google.com" , "dave.hansen@intel.com" , "luto@amacapital.net" , "jikos@kernel.org" , "gregkh@linux-foundation.org" In-Reply-To: <20180108050612.wmtwdbx44hmkf6au@treble> References: <1515058213.12987.89.camel@amazon.co.uk> <20180104143710.8961-1-dwmw@amazon.co.uk> <1515160619.29312.126.camel@amazon.co.uk> <1515170506.29312.149.camel@amazon.co.uk> <20180105164505.xpw5pefxsyu3z56e@pd.tnic> <20180105170806.mtylu2zagfxyj3ry@treble> <20180106003059.jhwx4ouc7xbt7yw6@pd.tnic> <20180108050612.wmtwdbx44hmkf6au@treble> Face: 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 Organization: Amazon Content-Type: multipart/signed; micalg=sha-256; protocol="application/x-pkcs7-signature"; boundary="=-PhCEERElzbOQWLHIDWF7" Date: Mon, 8 Jan 2018 07:55:20 +0000 X-Mailer: Evolution 3.18.5.2-0ubuntu3.2 MIME-Version: 1.0 From: "Woodhouse, David" X-Evolution-Source: 1481217574.17989.4@uc8d3ff76b9bc5848a9cc Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Return-Path: --=-PhCEERElzbOQWLHIDWF7 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sun, 2018-01-07 at 23:06 -0600, Josh Poimboeuf wrote: >=20 > Here's the use case I had in mind before.=C2=A0 With paravirt, >=20 > =C2=A0 ENABLE_INTERRUPTS(CLBR_NONE) >=20 > becomes >=20 > =C2=A0 push=C2=A0=C2=A0%rax > =C2=A0 call=C2=A0=C2=A0*pv_irq_ops.irq_enable > =C2=A0 pop=C2=A0=C2=A0=C2=A0%rax >=20 > and I wanted to apply those instructions with an alternative.=C2=A0 It > doesn't work currently because the 'call' isn't first. I believe Borislav has made that work... however, if you're literally doing the above then you'd be introducing new indirect branches which is precisely what I've been trying to eliminate. I believe I was told to stop prodding at pvops and just trust that they all get turned into *direct* jumps at runtime. For example the above call would not be literally 'call *pv_irq_ops.irq_enable', because by the time the pvops are patched we'd *know* the final value of the irq_enable method, and we'd turn it into a *direct* call instead. Do I need to start looking at pvops again? --=-PhCEERElzbOQWLHIDWF7 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 GOASNdFJbNdgx7UGF+il6kRGSle17LJZKMgRiLJXYjECwnGwdfLdN5SINWD5IC3yXY8d14Bq6DyD 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