Re: [Xen-devel] [PATCH v9 3/8] VMX: Properly handle pi when all the assigned devices are removed

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Gao, Chao
> Sent: Monday, February 27, 2017 9:46 AM
> 
> From: Feng Wu <feng.wu@xxxxxxxxx>
> 
> This patch handles some corner cases when the last assigned device
> is removed from the domain. In this case we should carefully handle
> pi descriptor and the per-cpu blocking list, to make sure:
> - all the PI descriptor are in the right state when next time a
> devices is assigned to the domain again.
> - No remaining vcpus of the domain in the per-cpu blocking list.
> 
> Here we call vmx_pi_unblock_vcpu() to remove the vCPU from the blocking list
> if it is on the list. However, this could happen when vmx_vcpu_block() is
> being called, hence we might incorrectly add the vCPU to the blocking list
> while the last devcie is detached from the domain. Consider that the situation
> can only occur when detaching the last device from the domain and it is not
> a frequent operation, so we use domain_pause before that, which is considered
> as an clean and maintainable solution for the situation.
> 
> Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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