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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 B161EC04E84 for ; Thu, 16 May 2019 02:06:13 +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 71DF820862 for ; Thu, 16 May 2019 02:06:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 71DF820862 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]:47045 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hR5me-0005ry-HV for qemu-devel@archiver.kernel.org; Wed, 15 May 2019 22:06:12 -0400 Received: from eggs.gnu.org ([209.51.188.92]:33039) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hR5lk-0005N2-KN for qemu-devel@nongnu.org; Wed, 15 May 2019 22:05:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hR5lg-0001Ox-Dj for qemu-devel@nongnu.org; Wed, 15 May 2019 22:05:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42335) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hR5lg-0001Ok-7d; Wed, 15 May 2019 22:05:12 -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 69EC3307D913; Thu, 16 May 2019 02:05:11 +0000 (UTC) Received: from xz-x1 (dhcp-15-205.nay.redhat.com [10.66.15.205]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 416F126552; Thu, 16 May 2019 02:05:03 +0000 (UTC) Date: Thu, 16 May 2019 10:05:01 +0800 From: Peter Xu To: Alex Williamson Message-ID: <20190516020501.GJ16681@xz-x1> References: <155785983236.11040.9618506134214930578.stgit@gimli.home> <20190514142203.430c106e@x1.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190514142203.430c106e@x1.home> User-Agent: Mutt/1.10.1 (2018-07-13) 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 [10.5.110.48]); Thu, 16 May 2019 02:05:11 +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: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , ehabkost@redhat.com, mst@redhat.com, qemu-devel@nongnu.org, qemu-stable@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 02:22:03PM -0600, Alex Williamson wrote: > On Tue, 14 May 2019 13:03:31 -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. > > > > Link: https://bugs.launchpad.net/qemu/+bug/1826422 > > Link: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03305.html > > This link is superseded by a v2 of the mainline patch: > > Link: https://lists.gnu.org/archive/html/qemu-devel/2019-05/msg03338.html > > I believe this patch is still the proper stable backport though. Also > to clarify, this patch should be gated on mainline acceptance of the > link above, but clearly there's no clean cherry-pick between mainline > and stable for this, so I'm proposing them in parallel. Thanks, Agreed. As long as the 4.1 patch can be accepted, this should be the correct patch for 4.0-stable AFAICT: Reviewed-by: Peter Xu Thanks, -- Peter Xu