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=-5.1 required=3.0 tests=FROM_EXCESS_BASE64, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,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 604E2C31E46 for ; Wed, 12 Jun 2019 09:10:57 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3A24F2063F for ; Wed, 12 Jun 2019 09:10:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3A24F2063F 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 ([::1]:57824 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1hazHU-0003YL-FM for qemu-devel@archiver.kernel.org; Wed, 12 Jun 2019 05:10:56 -0400 Received: from eggs.gnu.org ([209.51.188.92]:40859) by lists.gnu.org with esmtp (Exim 4.86_2) (envelope-from ) id 1haz98-0007Q9-Ay for qemu-devel@nongnu.org; Wed, 12 Jun 2019 05:02:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1haz94-0007kT-QW for qemu-devel@nongnu.org; Wed, 12 Jun 2019 05:02:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45516) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1haz94-0007iw-ED for qemu-devel@nongnu.org; Wed, 12 Jun 2019 05:02:14 -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 9B79C300183C; Wed, 12 Jun 2019 09:02:10 +0000 (UTC) Received: from redhat.com (unknown [10.34.246.191]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E8CE126FC1; Wed, 12 Jun 2019 09:01:54 +0000 (UTC) Date: Wed, 12 Jun 2019 11:01:50 +0200 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Paolo Bonzini Message-ID: <20190612090150.GD6897@redhat.com> References: <155786484688.13873.6037015630912983760.stgit@gimli.home> <20190528232626-mutt-send-email-mst@kernel.org> <694a140e-1415-2595-8e22-0834ee17139f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <694a140e-1415-2595-8e22-0834ee17139f@redhat.com> User-Agent: Mutt/1.11.4 (2019-03-13) 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 [10.5.110.40]); Wed, 12 Jun 2019 09:02:10 +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-4.1 v2] q35: Revert to kernel irqchip X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 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, "Michael S. Tsirkin" , qemu-devel@nongnu.org, peterx@redhat.com, Alex Williamson , rth@twiddle.net Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, Jun 03, 2019 at 10:06:06AM +0200, Paolo Bonzini wrote: > On 29/05/19 05:30, Michael S. Tsirkin wrote: > > On Tue, May 14, 2019 at 02:14:41PM -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 in the > >> pc-q35-4.1 machine and create a pc-q35-4.0.1 machine for the 4.0-stable > >> branch. 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 kernel irqchip. > >> > >> Link: https://bugs.launchpad.net/qemu/+bug/1826422 > >> Fixes: b2fc91db8447 ("q35: set split kernel irqchip as default") > >> Signed-off-by: Alex Williamson > > > > OK I guess but it's really a kvm patch. > > So I'd like Paolo to review and merge if appropriate. > > > > Can't say this makes me too happy. split irqchip > > has a bunch of advantages. > > Yeah, me too but I don't see an alternative. I'll merge it today. FYI in Fedora we've had another unrelated regression bug that was identified as caused by the split irqchip change. With a Windows 7 guest, the clock is way too fast, for every 1 second wallclock time, 15 seconds passes in the guest. See the bug for more info: https://bugzilla.redhat.com/show_bug.cgi?id=1704375 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 :|