From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41148) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gRgDZ-0006PQ-QE for qemu-devel@nongnu.org; Tue, 27 Nov 2018 11:28:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gRgDT-0003qA-Ui for qemu-devel@nongnu.org; Tue, 27 Nov 2018 11:28:08 -0500 Received: from mx1.redhat.com ([209.132.183.28]:58880) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gRgDS-0003ow-Do for qemu-devel@nongnu.org; Tue, 27 Nov 2018 11:28:03 -0500 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9C71B308626B for ; Tue, 27 Nov 2018 16:28:01 +0000 (UTC) Date: Tue, 27 Nov 2018 11:27:53 -0500 From: "Michael S. Tsirkin" Message-ID: <20181127112541-mutt-send-email-mst@kernel.org> References: <1543238443-4993-1-git-send-email-pbonzini@redhat.com> <20181126173604-mutt-send-email-mst@kernel.org> <6cd98ced-a043-18c0-3aa5-4cda15c76ec5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6cd98ced-a043-18c0-3aa5-4cda15c76ec5@redhat.com> Subject: Re: [Qemu-devel] [PATCH 0/5] vhost: enable for all targets List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: =?iso-8859-1?Q?Marc-Andr=E9?= Lureau , qemu-devel@nongnu.org On Tue, Nov 27, 2018 at 10:04:59AM +0100, Paolo Bonzini wrote: > On 26/11/18 23:43, Michael S. Tsirkin wrote: > > On Mon, Nov 26, 2018 at 02:20:38PM +0100, Paolo Bonzini wrote: > >> vhost does not have to be supported only if KVM is present, in fact > >> vhost-user does not even need any kind of kernel support. This series > >> changes this. The rationale is that, when vhost-user-test.c will be > >> converted to qgraph, it will be able to test vhost-user support > >> for virtio-mmio backend even on x86. > > > > The reason for limiting it to KVM was very simple: > > it has the same set of problems with ordering > > as mttcg. > > > > So I guess it's fine but I think we must then limit it > > to when tcg emits fence instructions. > > > > Otherwise we'll get subtle race conditions. > > Got it, I'll take a look. However, right now you _can_ use vhost with > tcg as long as e.g. qemu-system-x86_64 is compiled with KVM support, so > this patch is not changing anything in this respect; the bug is > independent of this series. > > Paolo > Well qemu built with KVM implies host architecture == guest architecture, right? That should ensure race conditions do not happen in a very hacky way. -- MST