Re: [PATCH] evtchn/Flask: pre-allocate node on send path

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 24/09/2020 11:53, Jan Beulich wrote:
> xmalloc() & Co may not be called with IRQs off, or else check_lock()
> will have its assertion trigger about locks getting acquired
> inconsistently. Re-arranging the locking in evtchn_send() doesn't seem
> very reasonable, especially since the per-channel lock was introduced to
> avoid acquiring the per-domain event lock on the send paths. Issue a
> second call to xsm_evtchn_send() instead, before acquiring the lock, to
> give XSM / Flask a chance to pre-allocate whatever it may need.
This is the sort of fall-out I was expecting when we decide to turn off 
the interrupts for big chunk of code. I couldn't find any at the time 
though...
Can you remind which caller of send_guest{global, vcpu}_virq() will call 
them with interrupts off?
Would it be possible to consider deferring the call to a softirq 
taslket? If so, this would allow us to turn the interrupts again.
Cheers,

--
Julien Grall