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Re: [Xen-devel] [PATCH 6/10] Allow vcpu to pause self

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 6/10] Allow vcpu to pause self
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 12 Jul 2007 08:44:56 +0100
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On 12/7/07 06:05, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

>> But after a further thinking, based on the fact that enter_state will force
>> a lazy context flush on all CPUs now, this interface can be abandoned
>> then.
>> 
> 
> Seems issue still existing. It's possible that force lazy context flush
> in enter_state is done before dom0/vcpu0 enters context switch,
> since softirq is sent out before pause. How to find a safe point where
> we know that dom0/vcpu0 is definitely switched out?

How about doing the whole suspend/resume in dom0/vcpu0 context? Why switch
to a softirq at all? You can force dom0/vcpu0 onto cpu0 temporarily by
wrapping the suspend/resume in a pair of calls to vcpu_set_affinity().

If your register save/restore across the low-level S3 entry/exit is
comprehensive, then it should be fine to do it in dom0/vcpu0 context.

 -- Keir


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