From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D597DC43457 for ; Mon, 12 Oct 2020 20:25:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7AE2120BED for ; Mon, 12 Oct 2020 20:25:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="bx/noJzE" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728661AbgJLUZG (ORCPT ); Mon, 12 Oct 2020 16:25:06 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37500 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728586AbgJLUZG (ORCPT ); Mon, 12 Oct 2020 16:25:06 -0400 Received: from merlin.infradead.org (merlin.infradead.org [IPv6:2001:8b0:10b:1231::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7958CC0613D0 for ; Mon, 12 Oct 2020 13:25:06 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=Mime-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=XJ9zrvsCwv69ZDl9bpOY62GKAZt081Ynj+CIOExAddY=; b=bx/noJzEE0gvXfUGEsiEB74Icv XT3fGL+c+5S0WnAmhO4KjTH227Pru3I1+BPCatOd80uY+a5YHFVWusGc5dH4G6rbAww40rPUFBX3W amWI5bviwPFUHPR/xVMaOmTIJKXSCN6W2q4nI0BbJGrRjfy5D1k2SZCcYnR1dWOVUE0QCW7AsFFRf ou2Ach4ROjfGDgW/QOSJZ1Oydnf5eyFJnttNXHiHhRXgMVNDU+EOwXGfYQ0Lhw4K+kTdljk2RuJ2N BGgAHpfhGZObMWbUhHtvtEY7kL+YTYWDA6GRIjCczmgxP0LRI92BDaE4XpviDQaSAgf2uOTOuBJA8 J8s42IaQ==; Received: from 54-240-197-232.amazon.com ([54.240.197.232] helo=freeip.amazon.com) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kS4NQ-0000Ah-HL; Mon, 12 Oct 2020 20:25:00 +0000 Message-ID: Subject: Re: PCI, isolcpus, and irq affinity From: David Woodhouse To: Thomas Gleixner , Chris Friesen , Bjorn Helgaas Cc: linux-pci@vger.kernel.org, Christoph Hellwig , Nitesh Narayan Lal Date: Mon, 12 Oct 2020 21:24:58 +0100 In-Reply-To: <87zh4rp7gg.fsf@nanos.tec.linutronix.de> References: <20201012165839.GA3732859@bjorn-Precision-5520> <87a6wrqqpf.fsf@nanos.tec.linutronix.de> <87zh4rp7gg.fsf@nanos.tec.linutronix.de> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/x-pkcs7-signature"; boundary="=-bKNfWKgi0wfXffgHr6Ob" X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by merlin.infradead.org. See http://www.infradead.org/rpr.html Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org --=-bKNfWKgi0wfXffgHr6Ob Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2020-10-12 at 21:31 +0200, Thomas Gleixner wrote: > > In this case could disk I/O submitted by one of those CPUs end up=20 > > interrupting another one? >=20 > On older kernels, yes. >=20 > X86 enforces effective single CPU affinity for interrupts since v4.15. Is that here to stay? Because it means that sending external interrupts in logical mode is kind of pointless, and we might as well do this... --- a/arch/x86/kernel/apic/x2apic_cluster.c +++ b/arch/x86/kernel/apic/x2apic_cluster.c @@ -187,3 +187,3 @@ static struct apic apic_x2apic_cluster __ro_after_init = =3D { .irq_delivery_mode =3D dest_Fixed, - .irq_dest_mode =3D 1, /* logical */ + .irq_dest_mode =3D 0, /* physical */ =20 @@ -205,3 +205,3 @@ static struct apic apic_x2apic_cluster __ro_after_init = =3D { =20 - .calc_dest_apicid =3D x2apic_calc_apicid, + .calc_dest_apicid =3D apic_default_calc_apicid, =20 And then a bunch of things which currently set x2apic_phys just because of *external* IRQ limitations, no longer have to, and can still benefit from multicast of IPIs to whole clusters at a time. --=-bKNfWKgi0wfXffgHr6Ob Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 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