From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50213) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fb88r-000135-Ja for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:34:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fb88o-00079O-FN for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:34:05 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:56324 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fb88o-00078h-Aq for qemu-devel@nongnu.org; Thu, 05 Jul 2018 13:34:02 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 4C6634021FC2 for ; Thu, 5 Jul 2018 17:34:01 +0000 (UTC) Date: Thu, 5 Jul 2018 20:34:00 +0300 From: "Michael S. Tsirkin" Message-ID: <20180705202215-mutt-send-email-mst@kernel.org> References: <20180705123929.GB16293@redhat.com> <20180705125231.GD16293@redhat.com> <20180705164343.GE16293@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] Byte ordering of VM Generation ID in Windows VMs List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek Cc: "Richard W.M. Jones" , qemu-devel@nongnu.org, berrange@redhat.com, jferlan@redhat.com On Thu, Jul 05, 2018 at 07:15:34PM +0200, Laszlo Ersek wrote: > > It has to be said that after reading the spec again [the MSFT spec, > > not qemu's spec] and what other hypervisors are doing, I'm not sure > > qemu is doing the right thing here. > > That's the thing about specs -- interpretation. I've read the vmgenid > spec several times as well, and I've always understood it as Microsoft > meaning UUID / GUID as a primary representation for VMGENID. I may have > been biased by UUID/GUID usage in UEFI. > > When the feature was being developed for QEMU, we struggled with the > interpretation of a good number of other bits as well; hence the > "Requirements" section of QEMU's spec: "this is how we understood it". > Without an open list to discuss things with Microsoft, sometimes we can > only guess what is a "likely faithful" interpretation, and test it in > practice. > > I still believe QEMU's current interpretation is the right one; but I > can't prove it. > > Laszlo Well it does seem that at least some guest code wants a counter there. So if someone posts a patch adding a count property there to be stored in LE format, plus a unit test - I'll merge it, even though it does not look like libvirt wants that. -- MST