Re: [Xen-devel] [PATCH v7 15/17] vmx: VT-d posted-interrupt core logic handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.09.15 at 09:19, <feng.wu@xxxxxxxxx> wrote:
> However, I do find some issues with my proposal above, see below:
> 
> 1. Set _VPF_blocked
> 2. ret = arch_block()
> 3. if ( ret || local_events_need_delivery() )
>       clear_bit(_VPF_blocked, &v->pause_flags);
> 
> After step #2, if ret == false, that means, we successfully changed the PI
> descriptor in arch_block(), if local_events_need_delivery() returns true,
> _VPF_blocked is cleared. After that, external interrupt come in, hence
> pi_wakeup_interrupt() --> vcpu_unblock(), but _VPF_blocked is cleared,
> so vcpu_unblock() does nothing, so the vCPU's PI state is incorrect.
> 
> One possible solution for it is:
> - Disable the interrupts before the check in step #3 above
> - if local_events_need_delivery() returns true, undo all the operations
>  done in arch_block()
> - Enable interrupts after _VPF_blocked gets cleared.

Couldn't this be taken care of by, if necessary, adjusting PI state
in vmx_do_resume()?

Jan


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