RE: [PATCH RFC] paravirt_ops: refactor struct paravirt_ops into smaller pv_*_ops

[Nakajima, Jun]

Jeremy Fitzhardinge wrote:
> Nakajima, Jun wrote:
> > Jeremy Fitzhardinge wrote:
> > 
> > 
> > > +	.pv_irq_ops = {
> > > +		 .init_IRQ = native_init_IRQ,
> > > +		 .save_fl = native_save_fl,
> > > +		 .restore_fl = native_restore_fl,
> > > +		 .irq_disable = native_irq_disable,
> > > +		 .irq_enable = native_irq_enable,
> > > +		 .safe_halt = native_safe_halt,
> > > +		 .halt = native_halt,
> > > +	 },
> > > 
> > 
> > I think the halt stuff should be moved to pv_cpu_ops?
> > 
> You mean halt's alternate "shutdown vcpu" meaning if you call it with
> interrupts disabled?  Yeah, I'd be happy to have an explicit op for
> that, rather than making it a secondary overloaded meaning.  And use
> "safe_halt" for all uses of "wait for next interrupt".

Yes. For the native, "safe_halt" is "sti; hlt". The "native_halt" is
just "hlt". So the para_virt part of "hlt" could be moved to pv_cpu_ops,
and the "sti" part stays in pv_irq_ops.

> 
> > > +	.pv_misc_ops = {
> > > +		 .set_lazy_mode = paravirt_nop,
> > > +	 },
> > > 
> > 
> > Or you can split it to pv_cpu_ops and pv_mmu_ops, assuming that they
> > don't need to interact with each other in terms of the lazy
handling.
> > 
> 
> You mean have separate lazy_mmu and lazy_cpu (lazy_context_switch)
ops?
> Possible, but they're still exclusive.  (I think VMI, at least,
assumes
> that you can't have lazy_mmu and lazy_cpu active at the same time, and
> its nice to enforce this in the interface.)

Okay I understand what you are saying.

> 
> But having a whole misc structure for this interface is pretty warty,
I
> admit.
> 
>     J

Actually my concern was that such misc ops might grow to include the
things don't fit well anywhere else. To me, then pv_lazy_ops (with just
.set_mode) might be better.

Jun
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Intel Open Source Technology Center
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