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Jones" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH 0/1] vmx: Fix mapping Message-ID: <20211004095912.GP7596@redhat.com> References: <20210929092044.GE3361@redhat.com> <20210929095719.GH3361@redhat.com> <20210929103400.GJ3361@redhat.com> <20210930073348.GL7596@redhat.com> <20210930091620.GX3361@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210930091620.GX3361@redhat.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=rjones@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=rjones@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.055, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: libvir-list@redhat.com, Michal Privoznik , qemu-devel@nongnu.org, armbru@redhat.com, acatan@amazon.com, lersek@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" It turns out that changing the qemu implementation is painful, particularly if we wish to maintain backwards compatibility of the command line and live migration. Instead I opted to document comprehensively what all the different hypervisors do: https://github.com/libguestfs/virt-v2v/blob/master/docs/vm-generation-id-across-hypervisors.txt On Thu, Sep 30, 2021 at 10:16:20AM +0100, Richard W.M. Jones wrote: > I was going to suggest something like: > > aa-bb-cc.. > or > aabbcc.. After thinking about this some more, the real implementation on Windows guest and host is two 64 bit little-endian integers[1]. How about implementing this exactly the same way as Hyper-V (and VMware): 0x8877665544332211 0x00ffeeddccbbaa99 This would have to be mapped to the following qemu command line: qemu -device vmgenid,guid=44332211-6655-8877-99aa-bbccddeeff00 which would unmangle to the following in guest physical memory: 11 22 33 44 55 66 77 88 99 aa bb cc dd ee ff 00 The equivalent back-compat option would be: 44332211-6655-8877-99aa-bbccddeeff00 Rich. [1] No one has ever thought what to do about big-endian guests. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-df lists disk usage of guests without needing to install any software inside the virtual machine. Supports Linux and Windows. http://people.redhat.com/~rjones/virt-df/