On 19.11.20 13:51, Alexander Graf wrote: > > > On 19.11.20 13:02, Christian Borntraeger wrote: >> >> On 16.11.20 16:34, Catangiu, Adrian Costin wrote: >>> - Background >>> >>> The VM Generation ID is a feature defined by Microsoft (paper: >>> http://go.microsoft.com/fwlink/?LinkId=260709) and supported by >>> multiple hypervisor vendors. >>> >>> The feature is required in virtualized environments by apps that work >>> with local copies/caches of world-unique data such as random values, >>> uuids, monotonically increasing counters, etc. >>> Such apps can be negatively affected by VM snapshotting when the VM >>> is either cloned or returned to an earlier point in time. >>> >>> The VM Generation ID is a simple concept meant to alleviate the issue >>> by providing a unique ID that changes each time the VM is restored >>> from a snapshot. The hw provided UUID value can be used to >>> differentiate between VMs or different generations of the same VM. >>> >>> - Problem >>> >>> The VM Generation ID is exposed through an ACPI device by multiple >>> hypervisor vendors but neither the vendors or upstream Linux have no >>> default driver for it leaving users to fend for themselves. >> >> I see that the qemu implementation is still under discussion. What is > > Uh, the ACPI Vmgenid device emulation is in QEMU since 2.9.0 :). Ah right. Found it. > >> the status of the other existing implementations. Do they already exist? >> In other words is ACPI a given? >> I think the majority of this driver could be used with just a different >> backend for platforms without ACPI so in any case we could factor out >> the backend (acpi, virtio, whatever) but if we are open we could maybe >> start with something else. > > I agree 100%. I don't think we really need a new framework in the kernel for that. We can just have for example an s390x specific driver that also provides the same notification mechanism through a device node that is also named "/dev/vmgenid", no? > > Or alternatively we can split the generic part of this driver as soon as a second one comes along and then have both driver include that generic logic. Yes. I think it is probably the best variant to check if we split this into a front end /back end or provide a new driver when we have something. > > The only piece where I'm unsure is how this will interact with CRIU. Can containers emulate ioctls and device nodes? > > > Alex > > > > Amazon Development Center Germany GmbH > Krausenstr. 38 > 10117 Berlin > Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss > Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B > Sitz: Berlin > Ust-ID: DE 289 237 879 > >
