Re: [Xen-devel] [PATCH] x86: extend runstate area updates

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 08/18/09 05:48, Jan Beulich wrote:
> In order to give guests a hint at whether their vCPU-s are currently
> scheduled (so they can e.g. adapt their behavior in spin loops), update
> the run state area (if registered) also when de-scheduling a vCPU.
>
> Also fix an oversight in the compat mode implementation of
> VCPUOP_register_runstate_memory_area.
>
> Please also consider for the 3.4 and 3.3 branches.
>   

BTW, this actually changes the documented behaviour of
register_runstate_memory_area:

 *  2. Only one shared area may be registered per VCPU. The shared area is
 *     updated by the hypervisor each time the VCPU is scheduled. Thus
 *     runstate.state will always be RUNSTATE_running and
 *     runstate.state_entry_time will indicate the system time at which the
 *     VCPU was last scheduled to run.

not that I think anything was relying on the old behaviour (indeed, it's
pretty unexpected behaviour).

    J

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