From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53476) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WFiaL-00066y-L4 for qemu-devel@nongnu.org; Tue, 18 Feb 2014 06:11:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WFiaF-0002vJ-MB for qemu-devel@nongnu.org; Tue, 18 Feb 2014 06:11:33 -0500 Received: from mx1.redhat.com ([209.132.183.28]:10912) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WFiaF-0002vF-ET for qemu-devel@nongnu.org; Tue, 18 Feb 2014 06:11:27 -0500 Date: Tue, 18 Feb 2014 13:16:15 +0200 From: "Michael S. Tsirkin" Message-ID: <20140218111615.GE8114@redhat.com> References: <20140218103828.GB8114@redhat.com> <5303390B.50903@redhat.com> <20140218105159.GD8114@redhat.com> <53033E6F.60700@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53033E6F.60700@redhat.com> Subject: Re: [Qemu-devel] hotplug: VM got stuck when attaching a pass-through device to the non-pass-through VM for the first time List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: "chenliang (T)" , Avi Kivity , "Huangweidong (C)" , Gleb Natapov , KVM , "Zhanghaoyu (A)" , Luonengjun , "qemu-devel@nongnu.org" , "Gonglei (Arei)" , "Gaowei (UVP)" On Tue, Feb 18, 2014 at 12:05:19PM +0100, Paolo Bonzini wrote: > Il 18/02/2014 11:51, Michael S. Tsirkin ha scritto: > >>> I agree it's either COW breaking or (similarly) locking pages that > >>> the guest hasn't touched yet. > >>> > >>> You can use prealloc or "-rt mlock=on" to avoid this problem. > >>> > >>> Paolo > >Or the new shared flag - IIRC shared VMAs don't do COW either. > > Only if the problem isn't locking and zeroing of untouched pages > (also, it is not upstream is it?). No but it's a small patch - part of vhost user patchset. > Can you make a profile with perf? > > Paolo