From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:46554) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dIz4u-0005xe-PX for qemu-devel@nongnu.org; Thu, 08 Jun 2017 11:10:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dIz4r-0005ZC-Fk for qemu-devel@nongnu.org; Thu, 08 Jun 2017 11:10:28 -0400 Date: Thu, 8 Jun 2017 16:10:20 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20170608151019.GB2700@work-vm> References: <20170608144106.GG25805@umbus.fritz.box> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170608144106.GG25805@umbus.fritz.box> Subject: Re: [Qemu-devel] unplug_request and migration List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson , jdenemar@redhat.com Cc: quintela@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org * David Gibson (david@gibson.dropbear.id.au) wrote: > Hi Dave & Juan, > > I'm hoping one of you can answer this. > > I'm currently grappling with (amongst other things) a pseries machine > racing a hot unplug operation with a migrate. There's various issues > with what interim state we need, and which bits of it need to be > migrated that I'm still investigating. But, there's a more general > question that I'm guessing must have already been addressed for x86. > > For any "soft" unplug device - i.e. using ->unplug_request, rather > than ->unplug, giving a device_del command will just ask the guest > nicely to release the device, with the completion of the unplug > happening only if and when the guest indicates it's ready for the > device to go away. AFAICT, the device_del command will return as soon > as the request is made, but if the guest is busy, the completion of > the hot unplug could take arbitrarily long. > > So, what happens if there's a migration in between the unplug_request > and the guest completing the unplug? How does libvirt (or whatever) > know whether to include the device on the destination machine command > line? No, I don't understand how that works. cc'ing in jdenemar for libvirt Dave > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK