On Thu, 6 Mar 2014 12:04:50 +0000, Robie Basak <robie.basak@xxxxxxxxxxxxx> wrote: > On Thu, Mar 06, 2014 at 12:44:57PM +0100, Laszlo Ersek wrote: > > If I understand correctly, the question is this: > > > > Given a hypervisor that doesn't support non-volatile UEFI variables > > (including BootOrder and Boot####), is it possible to automatically > > boot a carefully prepared VM image, made available as a fixed media > > device? > > > > The answer is "yes". See > > Right, but I think there is a subsequent problem. > > > It is expected that this default boot will load an operating system or > > a maintenance utility. If this is an operating system setup program it > > is then responsible for setting the requisite environment variables > > for subsequent boots. The platform firmware may also decide to recover > ^^^^^^^^^^^^^^^^ > > or set to a known set of boot options. > > It seems to me that the guest OS is permitted to assume that persistent > boot variables will work after first boot, for subsequent boots. > > So, for example, the guest OS might, on bootloader or kernel upgrade, > completely replace the boot mechanism, dropping the removable path and > replacing it with a fixed disk arrangement, setting boot variables > appropriately, and assume that it can reboot and everything will > continue to work. > > But if the host does not support non-volatile variables, then this will > break. Correct > This is why I'm suggesting that the specification mandate that the guest > OS shipped in a "portable disk image" as defined by the spec must not > make this assumption. Also correct... the installer must be aware of this constraint which is why it is part of the draft spec. > It's either this, or mandate that all hosts must support persistent > variables. I have no objection to that in principle, but since we have > no implementation currently, it seems easier to avoid this particular > roadblock by tweaking the spec in a way that nobody seems to care about > anyway. Right. I guess my position is that if persistent storage is not implemented then there are a number of install/upgrade scenarios that won't work. Regardless, portable images must assume an empty boot list and we can build that into the spec. g. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
