From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34017) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gZUIq-0000xf-9y for qemu-devel@nongnu.org; Wed, 19 Dec 2018 00:21:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gZUIn-0005n1-5g for qemu-devel@nongnu.org; Wed, 19 Dec 2018 00:21:52 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37406) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gZUIm-0005lW-Uu for qemu-devel@nongnu.org; Wed, 19 Dec 2018 00:21:49 -0500 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 2F14689AD8 for ; Wed, 19 Dec 2018 05:21:47 +0000 (UTC) Date: Wed, 19 Dec 2018 13:21:40 +0800 From: Peter Xu Message-ID: <20181219052140.GD16723@xz-x1> References: <20181217073114.11984-1-peterx@redhat.com> <20181217073114.11984-6-peterx@redhat.com> <20181218030713.GB16723@xz-x1> <54801de1-3617-0af0-43b1-952b2cc53623@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <54801de1-3617-0af0-43b1-952b2cc53623@redhat.com> Subject: Re: [Qemu-devel] [PATCH 5/5] intel_iommu: turn on IR by default List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , Jason Wang On Tue, Dec 18, 2018 at 01:30:23PM +0100, Paolo Bonzini wrote: > On 18/12/18 04:07, Peter Xu wrote: > > On Mon, Dec 17, 2018 at 03:31:14PM +0800, Peter Xu wrote: > >> IR has been there for a long time and long time no bug reported. > >> Let's turn it on by default to match general hardwares. Providing > >> compatibility bit for QEMU<=3.1. > >> > >> Signed-off-by: Peter Xu > > I forgot that IR will depend on split kernel irqchip and by default > > that's still "on" so "-M q35 -device intel-iommu" may not be able to > > boot correctly with all the default values and instead QEMU will ask > > user to turn on split irqchip. > > > > Paolo/Michael, do you think it would make any sense to turn the > > default kernel-irqchip machine parameter to split starting from qemu > > 4.0? Since AFAIU it should have little degradation to performance but > > at the same time it reduces kvm attack serface, which seems good. > > The main problem with that would be the minimal required kernel version, > which is 4.4 for split irqchip. But, we're already planning to make it > 4.5 so it's not an issue. Go for it. :) Thanks Paolo. :) I'll try to prepare a patch for it. Regards, -- Peter Xu