[PATCH v2] ARM/KVM: save and restore generic timer registers

[Peter Maydell]

On 20 June 2013 19:32, Christoffer Dall <christoffer.dall at linaro.org> wrote:
> Marc wrote:
>> So there is just one thing we absolutely need to make sure here: no vcpu
>> can run before they've all had their timer restored, and hence a stable
>> cntvoff. Otherwise two vcpus will have a different view of time.
>>
>> Can we guarantee this?

> Do we need to?  User space is free to modify time and all sort of other
> registers at any point during VM execution - it will just break the
> guest that it's running.

Note that QEMU will stop all CPUs before doing a migration or
similar operation. However there is a monitor command to query
the current CPU registers etc which won't try to stop the VM
first. So we might try to read vcpu registers (though I hope we
don't allow writing them).

-- PMM