Re: [Xen-devel] Question about VCPU's and VM's Blocked state

[George Dunlap <dunlapg@xxxxxxxxx>]

2010/1/19 Huibin QIAN <qianhb@xxxxxxxxxx>:
> I have some doubt about the vcpu scheduling in xen.
> what would make the vcpu be blocked?
> In HVM, does the hlt instruction make a vmexit and the hypervisor put the
> vcpu into sleep queue? Or anything else causes it? What about the PV?

HVM vcpus become blocked when they execute HLT.  PV vcpus become
blocked when they execute a SCHEDOP_block().  (See
xen/common/schedule.c).

By contrast, "offline" is the runstate that happens when the vcpu is
not runnable for any other reason; for example:
* While a domain is being constructed
* An HVM domain waiting for qemu to finish an emulated instruction (IO or MMIO)
* When a vcpu is flagged for scheduler migration to a different pcpu
* When a vcpu is being paused for another reason, for example during
live migration to another host.

> When we use 'xm list' we can get the vm state ,usually it is blocked or
> running, and what meaning is the blocked state?

Not sure about this one.  But there is no "sleep queue"; vcpus that
are blocked are simply not on the run queue (or running).

 -George

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