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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 52F94C04AB4 for ; Tue, 14 May 2019 19:38:29 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 258EF20881 for ; Tue, 14 May 2019 19:38:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 258EF20881 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([127.0.0.1]:53231 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hQdFs-0003K0-Ce for qemu-devel@archiver.kernel.org; Tue, 14 May 2019 15:38:28 -0400 Received: from eggs.gnu.org ([209.51.188.92]:53785) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hQdDn-0001vb-Ip for qemu-devel@nongnu.org; Tue, 14 May 2019 15:36:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hQdDm-0008HQ-EH for qemu-devel@nongnu.org; Tue, 14 May 2019 15:36:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46824) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hQdDm-0008GZ-8m; Tue, 14 May 2019 15:36:18 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C8FAB307D970; Tue, 14 May 2019 19:36:16 +0000 (UTC) Received: from x1.home (ovpn-117-92.phx2.redhat.com [10.3.117.92]) by smtp.corp.redhat.com (Postfix) with ESMTP id AE27B19C5B; Tue, 14 May 2019 19:36:11 +0000 (UTC) Date: Tue, 14 May 2019 13:36:11 -0600 From: Alex Williamson To: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" Message-ID: <20190514133611.3e2e166d@x1.home> In-Reply-To: <20190514192232.GB9512@redhat.com> References: <155785983236.11040.9618506134214930578.stgit@gimli.home> <20190514192232.GB9512@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Tue, 14 May 2019 19:36:16 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH for-4.0.1] q35: Revert to kernel irqchip X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: ehabkost@redhat.com, mst@redhat.com, qemu-stable@nongnu.org, peterx@redhat.com, qemu-devel@nongnu.org, pbonzini@redhat.com, rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Tue, 14 May 2019 20:22:32 +0100 Daniel P. Berrang=C3=A9 wrote: > On Tue, May 14, 2019 at 01:03:31PM -0600, Alex Williamson wrote: > > Commit b2fc91db8447 ("q35: set split kernel irqchip as default") changed > > the default for the pc-q35-4.0 machine type to use split irqchip, which > > turned out to have disasterous effects on vfio-pci INTx support. KVM > > resampling irqfds are registered for handling these interrupts, but > > these are non-functional in split irqchip mode. We can't simply test > > for split irqchip in QEMU as userspace handling of this interrupt is a > > significant performance regression versus KVM handling (GeForce GPUs > > assigned to Windows VMs are non-functional without forcing MSI mode or > > re-enabling kernel irqchip). > >=20 > > The resolution is to revert the change in default irqchip mode with a > > new pc-q35-4.0.1 machine type for qemu-stable while the development > > branch makes the same change in the pc-q35-4.1 machine type. The > > qemu-q35-4.0 machine type should not be used in vfio-pci configurations > > for devices requiring legacy INTx support without explicitly modifying > > the VM configuration to use KVM irqchip. This new 4.0.1 machine type > > makes this change automatically. =20 >=20 > If we introduce a pc-q35-4.0.1 machine type in -stable, then VMs > created in stable won't be migratable to future 4.1 unless we also > create this same machine type in master. Yes, I overlooked 4.0.1 on 4.1, I'm working on that now. Reposting a v2 of the 4.1 version shortly. > If we really want to create a new 4.0.1 machine type, then this > patch needs to go to git master before stable IMHO to guarantee > no regression to master. Yes, I'm doing both in parallel, I expect the 4.0.1 support to be contingent on be the master branch change, thus the second link below. Thanks, Alex > > Link: https://bugs.launchpad.net/qemu/+bug/1826422 > > Link: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03305.ht= ml > > Fixes: b2fc91db8447 ("q35: set split kernel irqchip as default") > > Cc: qemu-stable@nongnu.org > > Signed-off-by: Alex Williamson > > --- > >=20 > > Do we want new stable versions for other archs too or only as needed? = =20 >=20 >=20 >=20 > Regards, > Daniel