The problem is that you're choosing a random vcpu to run, without considering whether it *wants* to run or not.  In this case, you're running a vcpu before it's even been completely set up yet (write_cr3 is failing because the guest *has* no cr3 ready yet).

The normal way schedulers deal with this is to keep one list of all vcpus (or all domains), and another list with "runnable" vcpus.  You can keep track of which vcpus are runnable with the vcpu_wake() callback and by using vcpu_runnable() in schedule().

At very least, your loop in schedule should check vcpu_runnable() before selecting it.

-George

michele.paolino wrote:

Here's my random scheduler. It works until I start a virtual machine (error file attached is the serial console's log).
In xen call trace there isn't any of my functions.
To generate random numbers I'm using the hash (MD5) of NOW() function.
I would also Know why at boot time there are two calls at vcpu_init function for vcpu with id = 0 ??

Thanks
Michele