From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33895) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XONQT-0002Lg-29 for qemu-devel@nongnu.org; Mon, 01 Sep 2014 04:57:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XONQM-0000ZV-SR for qemu-devel@nongnu.org; Mon, 01 Sep 2014 04:57:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54008) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XONQM-0000ZQ-JA for qemu-devel@nongnu.org; Mon, 01 Sep 2014 04:57:18 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s818vHWJ011481 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Mon, 1 Sep 2014 04:57:17 -0400 Message-ID: <540434EA.8080203@redhat.com> Date: Mon, 01 Sep 2014 10:57:14 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1407670353-14971-1-git-send-email-ghammer@redhat.com> <1407670353-14971-3-git-send-email-ghammer@redhat.com> <53E7AA72.6030204@redhat.com> <53E9CA22.8090300@redhat.com> <53F07AB2.4070601@redhat.com> <54041E26.8070406@redhat.com> In-Reply-To: <54041E26.8070406@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/2] i386: Add a Virtual Machine Generation ID device. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gal Hammer , qemu-devel@nongnu.org Il 01/09/2014 09:20, Gal Hammer ha scritto: >> >> We are still in the process of defining which devices/methods go in the >> DSDT and which go in the SSDT. We had bad experiences with ACPI table >> migration in 2.1, and one plan to fix them is the following: >> >> * the DSDT should always be the same size no matter what command line >> options are there >> >> * the SSDT should have the exact same content (byte-for-byte) for >> different versions of QEMU, with the same command line options >> (including the machine type). >> >> Right now your code obeys the first rule, not the second rule, so it >> should add the device to the DSDT. > > Are you sure about selecting the DSDT? I don't see anyone else is using > the ACPI_EXTRACT_NAME_* macros in the DSDT table (and I keep crashing my > guest, but ignore it for now ;-)). There is one user: acpi-dsdt-isa.dsl: ACPI_EXTRACT_NAME_BYTE_CONST DSDT_APPLESMC_STA >> BTW, which events would cause the ID to change? How should live cloning >> (or revert to a disk+RAM snapshot) be implemented by layers above QEMU >> for the VM gen ID to be patched? Can you add something to docs/ about >> it? > > The VGID is expected to change when executing a VM with the -snapshot > option, when a VM is restored from a backup or when it is imported, > copied or cloned. So I would say it is a management's call. Ok, got it. So to support migration (which includes reverting to an earlier disk+RAM snapshot) you just need to ensure the VGID is patched accordingly. Whether VGID _will_ be different or not, that's management's call. > I think that the Microsoft's document describes the requirements better > than me :-). > >> Also, how does this ID compare to the UUID in the DMI info (-uuid)? > > The -uuid is not expected to change after the VM was created. Unlike the > -vmgenid that is designed to give the guest OS a notification that a > change has occurred. Microsoft, as an example, writes that is can be use > for a safer cryptographic software. I would say that cloning should change the UUID (and the VMGID). Paolo