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=-5.4 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, URIBL_BLOCKED,USER_AGENT_MUTT 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 AEA68C04AB4 for ; Tue, 14 May 2019 19:28:03 +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 7D96F2166E for ; Tue, 14 May 2019 19:28:03 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7D96F2166E 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]:53064 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hQd5m-0003JG-Me for qemu-devel@archiver.kernel.org; Tue, 14 May 2019 15:28:02 -0400 Received: from eggs.gnu.org ([209.51.188.92]:50454) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hQd0j-0007Gh-2T for qemu-devel@nongnu.org; Tue, 14 May 2019 15:22:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hQd0h-00045x-3f for qemu-devel@nongnu.org; Tue, 14 May 2019 15:22:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:51528) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hQd0f-0003pP-G6; Tue, 14 May 2019 15:22:45 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4DDC4300502A; Tue, 14 May 2019 19:22:42 +0000 (UTC) Received: from redhat.com (ovpn-112-28.ams2.redhat.com [10.36.112.28]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4B270608AB; Tue, 14 May 2019 19:22:34 +0000 (UTC) Date: Tue, 14 May 2019 20:22:32 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Alex Williamson Message-ID: <20190514192232.GB9512@redhat.com> References: <155785983236.11040.9618506134214930578.stgit@gimli.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <155785983236.11040.9618506134214930578.stgit@gimli.home> User-Agent: Mutt/1.11.4 (2019-03-13) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 14 May 2019 19:22:42 +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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= 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, 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). > > 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. 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. 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. > Link: https://bugs.launchpad.net/qemu/+bug/1826422 > Link: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03305.html > Fixes: b2fc91db8447 ("q35: set split kernel irqchip as default") > Cc: qemu-stable@nongnu.org > Signed-off-by: Alex Williamson > --- > > Do we want new stable versions for other archs too or only as needed? Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|