[Xen-devel] Re: [PATCH] passthrough: use tasklet to deliver interrupts

[Kouya Shimura <kouya@xxxxxxxxxxxxxx>]

Keir Fraser writes:
> You remove a set_time/stop_timer pair. Is this because it was just to handle
> arbitrary delay in calling hvm_dirq_assist() (which should no longer be
> possible as we use a tasklet)?

Yes. I think PT_IRQ_TIME_OUT(8msec) might be possible but can hardly happen.
Even if hvm_dirq_assist() is not executed within an arbitrary time, 
I think it is harmless. hvm_dirq_assist() will be certainly executed on
a VM exit. Strictly speeking, timer is also not guaranteed.

Actually I have observed 10msec delay from hvm_do_IRQ_dpci till
hvm_dirq_assist(). It is a special case caused by flush_tlb_mask().

> > Note: the change of raise_softirq (convert to macro from static inline)
> >  is needed for ia64 build.
> 
> That makes no sense. The function has been implemented (and used) in its
> existing form for a long time. Why would it suddenly break on ia64?

Since "#include <xen/softirq.h>" is added to xen/hvm/irq.h.
In ia64, smp_processor_id() refers a field of struct vcpu. 
It makes difficult to untie the nest of include.

Using a pointer to tasklet in struct hvm_irq_dpci helps to solve it.
But malloc/free is ugly...

Thanks,
Kouya

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