On 18/11/13 09:29, Jan Beulich wrote: >>>> On 15.11.13 at 21:07, David Vrabel <david.vrabel at citrix.com> wrote: >> On 15/11/13 15:56, Daniel Kiper wrote: >>> Clear unused registers before jumping into an image. This way >>> loaded image could not assume that any register has an specific >>> info about earlier running Xen hypervisor. However, it also >>> does not mean that the image may expect that a given register >>> is zeroed. The image MUST assume that every register has a random >>> value or in other words it is uninitialized or has undefined state. >> >> I think this, where the specification (registers undefined) differs from >> the implementation (registers zeroed), is the worst option. >> >> I also think it is more likely for an image to inadvertently rely on a >> zero value that whatever junk Xen has left behind. > > Preventing users to rely on anything would likely make it > desirable to put some random value into all unused registers. I don't think we need to go that far. I would just like to avoid someone looking that the implementation (and not the documentation) and concluding that zero-ing of the registers is part of the specified behaviour, or looking at the implementation and documentation and wondering why they don't agree. I really don't think there is anything more to be said on this. David
