[Xen-devel] Re: 0/4 Xen Scheduling Groups

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 12/5/07 01:16, "Mike D. Day" <ncmike@xxxxxxxxxx> wrote:

>>> After these first patches get accepted I plan on implementing a
>>> feature where one domain can tell the scheduler it would like to run
>>> *after* a different domain in the same group.
>>> 
>>> Xen already does this for dom0
>> 
>> Does it?
> 
> When an hvm domain does an emulated io, xen creates an event which is
> delivered to the idle domain (xen), which in turn triggers a soft
> interrupt on domain 0. In effect dom0 is immediately scheduled. Dom 0
> then emulates the io while the hvm domain is sleeping.

I thought we decoded the instruction to be emulated in Xen (in the context
of the HVM domain, so current==hvm-domain) then packaged it up in a
shared-memory page and notified qemu-dm in dom0 via an event channel. To my
knowledge there's no special treatment of this event channel or of dom0: the
notification is treated just like any wake-up of any arbitrary domain.

 -- Keir



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